1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie.
6 * kswapd added: 7.1.96 sct
7 * Removed kswapd_ctl limits, and swap out as many pages as needed
8 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
9 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
10 * Multiqueue VM started 5.8.00, Rik van Riel.
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
16 #include <linux/sched/mm.h>
17 #include <linux/module.h>
18 #include <linux/gfp.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/swap.h>
21 #include <linux/pagemap.h>
22 #include <linux/init.h>
23 #include <linux/highmem.h>
24 #include <linux/vmpressure.h>
25 #include <linux/vmstat.h>
26 #include <linux/file.h>
27 #include <linux/writeback.h>
28 #include <linux/blkdev.h>
29 #include <linux/buffer_head.h> /* for try_to_release_page(),
30 buffer_heads_over_limit */
31 #include <linux/mm_inline.h>
32 #include <linux/backing-dev.h>
33 #include <linux/rmap.h>
34 #include <linux/topology.h>
35 #include <linux/cpu.h>
36 #include <linux/cpuset.h>
37 #include <linux/compaction.h>
38 #include <linux/notifier.h>
39 #include <linux/rwsem.h>
40 #include <linux/delay.h>
41 #include <linux/kthread.h>
42 #include <linux/freezer.h>
43 #include <linux/memcontrol.h>
44 #include <linux/delayacct.h>
45 #include <linux/sysctl.h>
46 #include <linux/oom.h>
47 #include <linux/pagevec.h>
48 #include <linux/prefetch.h>
49 #include <linux/printk.h>
50 #include <linux/dax.h>
51 #include <linux/psi.h>
53 #include <asm/tlbflush.h>
54 #include <asm/div64.h>
56 #include <linux/swapops.h>
57 #include <linux/balloon_compaction.h>
61 #define CREATE_TRACE_POINTS
62 #include <trace/events/vmscan.h>
65 /* How many pages shrink_list() should reclaim */
66 unsigned long nr_to_reclaim
;
69 * Nodemask of nodes allowed by the caller. If NULL, all nodes
75 * The memory cgroup that hit its limit and as a result is the
76 * primary target of this reclaim invocation.
78 struct mem_cgroup
*target_mem_cgroup
;
81 * Scan pressure balancing between anon and file LRUs
83 unsigned long anon_cost
;
84 unsigned long file_cost
;
86 /* Can active pages be deactivated as part of reclaim? */
87 #define DEACTIVATE_ANON 1
88 #define DEACTIVATE_FILE 2
89 unsigned int may_deactivate
:2;
90 unsigned int force_deactivate
:1;
91 unsigned int skipped_deactivate
:1;
93 /* Writepage batching in laptop mode; RECLAIM_WRITE */
94 unsigned int may_writepage
:1;
96 /* Can mapped pages be reclaimed? */
97 unsigned int may_unmap
:1;
99 /* Can pages be swapped as part of reclaim? */
100 unsigned int may_swap
:1;
103 * Cgroup memory below memory.low is protected as long as we
104 * don't threaten to OOM. If any cgroup is reclaimed at
105 * reduced force or passed over entirely due to its memory.low
106 * setting (memcg_low_skipped), and nothing is reclaimed as a
107 * result, then go back for one more cycle that reclaims the protected
108 * memory (memcg_low_reclaim) to avert OOM.
110 unsigned int memcg_low_reclaim
:1;
111 unsigned int memcg_low_skipped
:1;
113 unsigned int hibernation_mode
:1;
115 /* One of the zones is ready for compaction */
116 unsigned int compaction_ready
:1;
118 /* There is easily reclaimable cold cache in the current node */
119 unsigned int cache_trim_mode
:1;
121 /* The file pages on the current node are dangerously low */
122 unsigned int file_is_tiny
:1;
124 /* Allocation order */
127 /* Scan (total_size >> priority) pages at once */
130 /* The highest zone to isolate pages for reclaim from */
133 /* This context's GFP mask */
136 /* Incremented by the number of inactive pages that were scanned */
137 unsigned long nr_scanned
;
139 /* Number of pages freed so far during a call to shrink_zones() */
140 unsigned long nr_reclaimed
;
144 unsigned int unqueued_dirty
;
145 unsigned int congested
;
146 unsigned int writeback
;
147 unsigned int immediate
;
148 unsigned int file_taken
;
152 /* for recording the reclaimed slab by now */
153 struct reclaim_state reclaim_state
;
156 #ifdef ARCH_HAS_PREFETCHW
157 #define prefetchw_prev_lru_page(_page, _base, _field) \
159 if ((_page)->lru.prev != _base) { \
162 prev = lru_to_page(&(_page->lru)); \
163 prefetchw(&prev->_field); \
167 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
171 * From 0 .. 200. Higher means more swappy.
173 int vm_swappiness
= 60;
175 static void set_task_reclaim_state(struct task_struct
*task
,
176 struct reclaim_state
*rs
)
178 /* Check for an overwrite */
179 WARN_ON_ONCE(rs
&& task
->reclaim_state
);
181 /* Check for the nulling of an already-nulled member */
182 WARN_ON_ONCE(!rs
&& !task
->reclaim_state
);
184 task
->reclaim_state
= rs
;
187 static LIST_HEAD(shrinker_list
);
188 static DECLARE_RWSEM(shrinker_rwsem
);
191 static int shrinker_nr_max
;
193 /* The shrinker_info is expanded in a batch of BITS_PER_LONG */
194 static inline int shrinker_map_size(int nr_items
)
196 return (DIV_ROUND_UP(nr_items
, BITS_PER_LONG
) * sizeof(unsigned long));
199 static inline int shrinker_defer_size(int nr_items
)
201 return (round_up(nr_items
, BITS_PER_LONG
) * sizeof(atomic_long_t
));
204 static struct shrinker_info
*shrinker_info_protected(struct mem_cgroup
*memcg
,
207 return rcu_dereference_protected(memcg
->nodeinfo
[nid
]->shrinker_info
,
208 lockdep_is_held(&shrinker_rwsem
));
211 static int expand_one_shrinker_info(struct mem_cgroup
*memcg
,
212 int map_size
, int defer_size
,
213 int old_map_size
, int old_defer_size
)
215 struct shrinker_info
*new, *old
;
216 struct mem_cgroup_per_node
*pn
;
218 int size
= map_size
+ defer_size
;
221 pn
= memcg
->nodeinfo
[nid
];
222 old
= shrinker_info_protected(memcg
, nid
);
223 /* Not yet online memcg */
227 new = kvmalloc_node(sizeof(*new) + size
, GFP_KERNEL
, nid
);
231 new->nr_deferred
= (atomic_long_t
*)(new + 1);
232 new->map
= (void *)new->nr_deferred
+ defer_size
;
234 /* map: set all old bits, clear all new bits */
235 memset(new->map
, (int)0xff, old_map_size
);
236 memset((void *)new->map
+ old_map_size
, 0, map_size
- old_map_size
);
237 /* nr_deferred: copy old values, clear all new values */
238 memcpy(new->nr_deferred
, old
->nr_deferred
, old_defer_size
);
239 memset((void *)new->nr_deferred
+ old_defer_size
, 0,
240 defer_size
- old_defer_size
);
242 rcu_assign_pointer(pn
->shrinker_info
, new);
243 kvfree_rcu(old
, rcu
);
249 void free_shrinker_info(struct mem_cgroup
*memcg
)
251 struct mem_cgroup_per_node
*pn
;
252 struct shrinker_info
*info
;
256 pn
= memcg
->nodeinfo
[nid
];
257 info
= rcu_dereference_protected(pn
->shrinker_info
, true);
259 rcu_assign_pointer(pn
->shrinker_info
, NULL
);
263 int alloc_shrinker_info(struct mem_cgroup
*memcg
)
265 struct shrinker_info
*info
;
266 int nid
, size
, ret
= 0;
267 int map_size
, defer_size
= 0;
269 down_write(&shrinker_rwsem
);
270 map_size
= shrinker_map_size(shrinker_nr_max
);
271 defer_size
= shrinker_defer_size(shrinker_nr_max
);
272 size
= map_size
+ defer_size
;
274 info
= kvzalloc_node(sizeof(*info
) + size
, GFP_KERNEL
, nid
);
276 free_shrinker_info(memcg
);
280 info
->nr_deferred
= (atomic_long_t
*)(info
+ 1);
281 info
->map
= (void *)info
->nr_deferred
+ defer_size
;
282 rcu_assign_pointer(memcg
->nodeinfo
[nid
]->shrinker_info
, info
);
284 up_write(&shrinker_rwsem
);
289 static inline bool need_expand(int nr_max
)
291 return round_up(nr_max
, BITS_PER_LONG
) >
292 round_up(shrinker_nr_max
, BITS_PER_LONG
);
295 static int expand_shrinker_info(int new_id
)
298 int new_nr_max
= new_id
+ 1;
299 int map_size
, defer_size
= 0;
300 int old_map_size
, old_defer_size
= 0;
301 struct mem_cgroup
*memcg
;
303 if (!need_expand(new_nr_max
))
306 if (!root_mem_cgroup
)
309 lockdep_assert_held(&shrinker_rwsem
);
311 map_size
= shrinker_map_size(new_nr_max
);
312 defer_size
= shrinker_defer_size(new_nr_max
);
313 old_map_size
= shrinker_map_size(shrinker_nr_max
);
314 old_defer_size
= shrinker_defer_size(shrinker_nr_max
);
316 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
318 ret
= expand_one_shrinker_info(memcg
, map_size
, defer_size
,
319 old_map_size
, old_defer_size
);
321 mem_cgroup_iter_break(NULL
, memcg
);
324 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)) != NULL
);
327 shrinker_nr_max
= new_nr_max
;
332 void set_shrinker_bit(struct mem_cgroup
*memcg
, int nid
, int shrinker_id
)
334 if (shrinker_id
>= 0 && memcg
&& !mem_cgroup_is_root(memcg
)) {
335 struct shrinker_info
*info
;
338 info
= rcu_dereference(memcg
->nodeinfo
[nid
]->shrinker_info
);
339 /* Pairs with smp mb in shrink_slab() */
340 smp_mb__before_atomic();
341 set_bit(shrinker_id
, info
->map
);
346 static DEFINE_IDR(shrinker_idr
);
348 static int prealloc_memcg_shrinker(struct shrinker
*shrinker
)
350 int id
, ret
= -ENOMEM
;
352 if (mem_cgroup_disabled())
355 down_write(&shrinker_rwsem
);
356 /* This may call shrinker, so it must use down_read_trylock() */
357 id
= idr_alloc(&shrinker_idr
, shrinker
, 0, 0, GFP_KERNEL
);
361 if (id
>= shrinker_nr_max
) {
362 if (expand_shrinker_info(id
)) {
363 idr_remove(&shrinker_idr
, id
);
370 up_write(&shrinker_rwsem
);
374 static void unregister_memcg_shrinker(struct shrinker
*shrinker
)
376 int id
= shrinker
->id
;
380 lockdep_assert_held(&shrinker_rwsem
);
382 idr_remove(&shrinker_idr
, id
);
385 static long xchg_nr_deferred_memcg(int nid
, struct shrinker
*shrinker
,
386 struct mem_cgroup
*memcg
)
388 struct shrinker_info
*info
;
390 info
= shrinker_info_protected(memcg
, nid
);
391 return atomic_long_xchg(&info
->nr_deferred
[shrinker
->id
], 0);
394 static long add_nr_deferred_memcg(long nr
, int nid
, struct shrinker
*shrinker
,
395 struct mem_cgroup
*memcg
)
397 struct shrinker_info
*info
;
399 info
= shrinker_info_protected(memcg
, nid
);
400 return atomic_long_add_return(nr
, &info
->nr_deferred
[shrinker
->id
]);
403 void reparent_shrinker_deferred(struct mem_cgroup
*memcg
)
407 struct mem_cgroup
*parent
;
408 struct shrinker_info
*child_info
, *parent_info
;
410 parent
= parent_mem_cgroup(memcg
);
412 parent
= root_mem_cgroup
;
414 /* Prevent from concurrent shrinker_info expand */
415 down_read(&shrinker_rwsem
);
417 child_info
= shrinker_info_protected(memcg
, nid
);
418 parent_info
= shrinker_info_protected(parent
, nid
);
419 for (i
= 0; i
< shrinker_nr_max
; i
++) {
420 nr
= atomic_long_read(&child_info
->nr_deferred
[i
]);
421 atomic_long_add(nr
, &parent_info
->nr_deferred
[i
]);
424 up_read(&shrinker_rwsem
);
427 static bool cgroup_reclaim(struct scan_control
*sc
)
429 return sc
->target_mem_cgroup
;
433 * writeback_throttling_sane - is the usual dirty throttling mechanism available?
434 * @sc: scan_control in question
436 * The normal page dirty throttling mechanism in balance_dirty_pages() is
437 * completely broken with the legacy memcg and direct stalling in
438 * shrink_page_list() is used for throttling instead, which lacks all the
439 * niceties such as fairness, adaptive pausing, bandwidth proportional
440 * allocation and configurability.
442 * This function tests whether the vmscan currently in progress can assume
443 * that the normal dirty throttling mechanism is operational.
445 static bool writeback_throttling_sane(struct scan_control
*sc
)
447 if (!cgroup_reclaim(sc
))
449 #ifdef CONFIG_CGROUP_WRITEBACK
450 if (cgroup_subsys_on_dfl(memory_cgrp_subsys
))
456 static int prealloc_memcg_shrinker(struct shrinker
*shrinker
)
461 static void unregister_memcg_shrinker(struct shrinker
*shrinker
)
465 static long xchg_nr_deferred_memcg(int nid
, struct shrinker
*shrinker
,
466 struct mem_cgroup
*memcg
)
471 static long add_nr_deferred_memcg(long nr
, int nid
, struct shrinker
*shrinker
,
472 struct mem_cgroup
*memcg
)
477 static bool cgroup_reclaim(struct scan_control
*sc
)
482 static bool writeback_throttling_sane(struct scan_control
*sc
)
488 static long xchg_nr_deferred(struct shrinker
*shrinker
,
489 struct shrink_control
*sc
)
493 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
))
497 (shrinker
->flags
& SHRINKER_MEMCG_AWARE
))
498 return xchg_nr_deferred_memcg(nid
, shrinker
,
501 return atomic_long_xchg(&shrinker
->nr_deferred
[nid
], 0);
505 static long add_nr_deferred(long nr
, struct shrinker
*shrinker
,
506 struct shrink_control
*sc
)
510 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
))
514 (shrinker
->flags
& SHRINKER_MEMCG_AWARE
))
515 return add_nr_deferred_memcg(nr
, nid
, shrinker
,
518 return atomic_long_add_return(nr
, &shrinker
->nr_deferred
[nid
]);
522 * This misses isolated pages which are not accounted for to save counters.
523 * As the data only determines if reclaim or compaction continues, it is
524 * not expected that isolated pages will be a dominating factor.
526 unsigned long zone_reclaimable_pages(struct zone
*zone
)
530 nr
= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_FILE
) +
531 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_FILE
);
532 if (get_nr_swap_pages() > 0)
533 nr
+= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_ANON
) +
534 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_ANON
);
540 * lruvec_lru_size - Returns the number of pages on the given LRU list.
541 * @lruvec: lru vector
543 * @zone_idx: zones to consider (use MAX_NR_ZONES for the whole LRU list)
545 static unsigned long lruvec_lru_size(struct lruvec
*lruvec
, enum lru_list lru
,
548 unsigned long size
= 0;
551 for (zid
= 0; zid
<= zone_idx
&& zid
< MAX_NR_ZONES
; zid
++) {
552 struct zone
*zone
= &lruvec_pgdat(lruvec
)->node_zones
[zid
];
554 if (!managed_zone(zone
))
557 if (!mem_cgroup_disabled())
558 size
+= mem_cgroup_get_zone_lru_size(lruvec
, lru
, zid
);
560 size
+= zone_page_state(zone
, NR_ZONE_LRU_BASE
+ lru
);
566 * Add a shrinker callback to be called from the vm.
568 int prealloc_shrinker(struct shrinker
*shrinker
)
573 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
) {
574 err
= prealloc_memcg_shrinker(shrinker
);
578 shrinker
->flags
&= ~SHRINKER_MEMCG_AWARE
;
581 size
= sizeof(*shrinker
->nr_deferred
);
582 if (shrinker
->flags
& SHRINKER_NUMA_AWARE
)
585 shrinker
->nr_deferred
= kzalloc(size
, GFP_KERNEL
);
586 if (!shrinker
->nr_deferred
)
592 void free_prealloced_shrinker(struct shrinker
*shrinker
)
594 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
) {
595 down_write(&shrinker_rwsem
);
596 unregister_memcg_shrinker(shrinker
);
597 up_write(&shrinker_rwsem
);
601 kfree(shrinker
->nr_deferred
);
602 shrinker
->nr_deferred
= NULL
;
605 void register_shrinker_prepared(struct shrinker
*shrinker
)
607 down_write(&shrinker_rwsem
);
608 list_add_tail(&shrinker
->list
, &shrinker_list
);
609 shrinker
->flags
|= SHRINKER_REGISTERED
;
610 up_write(&shrinker_rwsem
);
613 int register_shrinker(struct shrinker
*shrinker
)
615 int err
= prealloc_shrinker(shrinker
);
619 register_shrinker_prepared(shrinker
);
622 EXPORT_SYMBOL(register_shrinker
);
627 void unregister_shrinker(struct shrinker
*shrinker
)
629 if (!(shrinker
->flags
& SHRINKER_REGISTERED
))
632 down_write(&shrinker_rwsem
);
633 list_del(&shrinker
->list
);
634 shrinker
->flags
&= ~SHRINKER_REGISTERED
;
635 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
)
636 unregister_memcg_shrinker(shrinker
);
637 up_write(&shrinker_rwsem
);
639 kfree(shrinker
->nr_deferred
);
640 shrinker
->nr_deferred
= NULL
;
642 EXPORT_SYMBOL(unregister_shrinker
);
644 #define SHRINK_BATCH 128
646 static unsigned long do_shrink_slab(struct shrink_control
*shrinkctl
,
647 struct shrinker
*shrinker
, int priority
)
649 unsigned long freed
= 0;
650 unsigned long long delta
;
655 long batch_size
= shrinker
->batch
? shrinker
->batch
657 long scanned
= 0, next_deferred
;
659 freeable
= shrinker
->count_objects(shrinker
, shrinkctl
);
660 if (freeable
== 0 || freeable
== SHRINK_EMPTY
)
664 * copy the current shrinker scan count into a local variable
665 * and zero it so that other concurrent shrinker invocations
666 * don't also do this scanning work.
668 nr
= xchg_nr_deferred(shrinker
, shrinkctl
);
670 if (shrinker
->seeks
) {
671 delta
= freeable
>> priority
;
673 do_div(delta
, shrinker
->seeks
);
676 * These objects don't require any IO to create. Trim
677 * them aggressively under memory pressure to keep
678 * them from causing refetches in the IO caches.
680 delta
= freeable
/ 2;
683 total_scan
= nr
>> priority
;
685 total_scan
= min(total_scan
, (2 * freeable
));
687 trace_mm_shrink_slab_start(shrinker
, shrinkctl
, nr
,
688 freeable
, delta
, total_scan
, priority
);
691 * Normally, we should not scan less than batch_size objects in one
692 * pass to avoid too frequent shrinker calls, but if the slab has less
693 * than batch_size objects in total and we are really tight on memory,
694 * we will try to reclaim all available objects, otherwise we can end
695 * up failing allocations although there are plenty of reclaimable
696 * objects spread over several slabs with usage less than the
699 * We detect the "tight on memory" situations by looking at the total
700 * number of objects we want to scan (total_scan). If it is greater
701 * than the total number of objects on slab (freeable), we must be
702 * scanning at high prio and therefore should try to reclaim as much as
705 while (total_scan
>= batch_size
||
706 total_scan
>= freeable
) {
708 unsigned long nr_to_scan
= min(batch_size
, total_scan
);
710 shrinkctl
->nr_to_scan
= nr_to_scan
;
711 shrinkctl
->nr_scanned
= nr_to_scan
;
712 ret
= shrinker
->scan_objects(shrinker
, shrinkctl
);
713 if (ret
== SHRINK_STOP
)
717 count_vm_events(SLABS_SCANNED
, shrinkctl
->nr_scanned
);
718 total_scan
-= shrinkctl
->nr_scanned
;
719 scanned
+= shrinkctl
->nr_scanned
;
725 * The deferred work is increased by any new work (delta) that wasn't
726 * done, decreased by old deferred work that was done now.
728 * And it is capped to two times of the freeable items.
730 next_deferred
= max_t(long, (nr
+ delta
- scanned
), 0);
731 next_deferred
= min(next_deferred
, (2 * freeable
));
734 * move the unused scan count back into the shrinker in a
735 * manner that handles concurrent updates.
737 new_nr
= add_nr_deferred(next_deferred
, shrinker
, shrinkctl
);
739 trace_mm_shrink_slab_end(shrinker
, shrinkctl
->nid
, freed
, nr
, new_nr
, total_scan
);
744 static unsigned long shrink_slab_memcg(gfp_t gfp_mask
, int nid
,
745 struct mem_cgroup
*memcg
, int priority
)
747 struct shrinker_info
*info
;
748 unsigned long ret
, freed
= 0;
751 if (!mem_cgroup_online(memcg
))
754 if (!down_read_trylock(&shrinker_rwsem
))
757 info
= shrinker_info_protected(memcg
, nid
);
761 for_each_set_bit(i
, info
->map
, shrinker_nr_max
) {
762 struct shrink_control sc
= {
763 .gfp_mask
= gfp_mask
,
767 struct shrinker
*shrinker
;
769 shrinker
= idr_find(&shrinker_idr
, i
);
770 if (unlikely(!shrinker
|| !(shrinker
->flags
& SHRINKER_REGISTERED
))) {
772 clear_bit(i
, info
->map
);
776 /* Call non-slab shrinkers even though kmem is disabled */
777 if (!memcg_kmem_enabled() &&
778 !(shrinker
->flags
& SHRINKER_NONSLAB
))
781 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
782 if (ret
== SHRINK_EMPTY
) {
783 clear_bit(i
, info
->map
);
785 * After the shrinker reported that it had no objects to
786 * free, but before we cleared the corresponding bit in
787 * the memcg shrinker map, a new object might have been
788 * added. To make sure, we have the bit set in this
789 * case, we invoke the shrinker one more time and reset
790 * the bit if it reports that it is not empty anymore.
791 * The memory barrier here pairs with the barrier in
792 * set_shrinker_bit():
794 * list_lru_add() shrink_slab_memcg()
795 * list_add_tail() clear_bit()
797 * set_bit() do_shrink_slab()
799 smp_mb__after_atomic();
800 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
801 if (ret
== SHRINK_EMPTY
)
804 set_shrinker_bit(memcg
, nid
, i
);
808 if (rwsem_is_contended(&shrinker_rwsem
)) {
814 up_read(&shrinker_rwsem
);
817 #else /* CONFIG_MEMCG */
818 static unsigned long shrink_slab_memcg(gfp_t gfp_mask
, int nid
,
819 struct mem_cgroup
*memcg
, int priority
)
823 #endif /* CONFIG_MEMCG */
826 * shrink_slab - shrink slab caches
827 * @gfp_mask: allocation context
828 * @nid: node whose slab caches to target
829 * @memcg: memory cgroup whose slab caches to target
830 * @priority: the reclaim priority
832 * Call the shrink functions to age shrinkable caches.
834 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
835 * unaware shrinkers will receive a node id of 0 instead.
837 * @memcg specifies the memory cgroup to target. Unaware shrinkers
838 * are called only if it is the root cgroup.
840 * @priority is sc->priority, we take the number of objects and >> by priority
841 * in order to get the scan target.
843 * Returns the number of reclaimed slab objects.
845 static unsigned long shrink_slab(gfp_t gfp_mask
, int nid
,
846 struct mem_cgroup
*memcg
,
849 unsigned long ret
, freed
= 0;
850 struct shrinker
*shrinker
;
853 * The root memcg might be allocated even though memcg is disabled
854 * via "cgroup_disable=memory" boot parameter. This could make
855 * mem_cgroup_is_root() return false, then just run memcg slab
856 * shrink, but skip global shrink. This may result in premature
859 if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg
))
860 return shrink_slab_memcg(gfp_mask
, nid
, memcg
, priority
);
862 if (!down_read_trylock(&shrinker_rwsem
))
865 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
866 struct shrink_control sc
= {
867 .gfp_mask
= gfp_mask
,
872 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
873 if (ret
== SHRINK_EMPTY
)
877 * Bail out if someone want to register a new shrinker to
878 * prevent the registration from being stalled for long periods
879 * by parallel ongoing shrinking.
881 if (rwsem_is_contended(&shrinker_rwsem
)) {
887 up_read(&shrinker_rwsem
);
893 void drop_slab_node(int nid
)
898 struct mem_cgroup
*memcg
= NULL
;
900 if (fatal_signal_pending(current
))
904 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
906 freed
+= shrink_slab(GFP_KERNEL
, nid
, memcg
, 0);
907 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)) != NULL
);
908 } while (freed
> 10);
915 for_each_online_node(nid
)
919 static inline int is_page_cache_freeable(struct page
*page
)
922 * A freeable page cache page is referenced only by the caller
923 * that isolated the page, the page cache and optional buffer
924 * heads at page->private.
926 int page_cache_pins
= thp_nr_pages(page
);
927 return page_count(page
) - page_has_private(page
) == 1 + page_cache_pins
;
930 static int may_write_to_inode(struct inode
*inode
)
932 if (current
->flags
& PF_SWAPWRITE
)
934 if (!inode_write_congested(inode
))
936 if (inode_to_bdi(inode
) == current
->backing_dev_info
)
942 * We detected a synchronous write error writing a page out. Probably
943 * -ENOSPC. We need to propagate that into the address_space for a subsequent
944 * fsync(), msync() or close().
946 * The tricky part is that after writepage we cannot touch the mapping: nothing
947 * prevents it from being freed up. But we have a ref on the page and once
948 * that page is locked, the mapping is pinned.
950 * We're allowed to run sleeping lock_page() here because we know the caller has
953 static void handle_write_error(struct address_space
*mapping
,
954 struct page
*page
, int error
)
957 if (page_mapping(page
) == mapping
)
958 mapping_set_error(mapping
, error
);
962 /* possible outcome of pageout() */
964 /* failed to write page out, page is locked */
966 /* move page to the active list, page is locked */
968 /* page has been sent to the disk successfully, page is unlocked */
970 /* page is clean and locked */
975 * pageout is called by shrink_page_list() for each dirty page.
976 * Calls ->writepage().
978 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
)
981 * If the page is dirty, only perform writeback if that write
982 * will be non-blocking. To prevent this allocation from being
983 * stalled by pagecache activity. But note that there may be
984 * stalls if we need to run get_block(). We could test
985 * PagePrivate for that.
987 * If this process is currently in __generic_file_write_iter() against
988 * this page's queue, we can perform writeback even if that
991 * If the page is swapcache, write it back even if that would
992 * block, for some throttling. This happens by accident, because
993 * swap_backing_dev_info is bust: it doesn't reflect the
994 * congestion state of the swapdevs. Easy to fix, if needed.
996 if (!is_page_cache_freeable(page
))
1000 * Some data journaling orphaned pages can have
1001 * page->mapping == NULL while being dirty with clean buffers.
1003 if (page_has_private(page
)) {
1004 if (try_to_free_buffers(page
)) {
1005 ClearPageDirty(page
);
1006 pr_info("%s: orphaned page\n", __func__
);
1012 if (mapping
->a_ops
->writepage
== NULL
)
1013 return PAGE_ACTIVATE
;
1014 if (!may_write_to_inode(mapping
->host
))
1017 if (clear_page_dirty_for_io(page
)) {
1019 struct writeback_control wbc
= {
1020 .sync_mode
= WB_SYNC_NONE
,
1021 .nr_to_write
= SWAP_CLUSTER_MAX
,
1023 .range_end
= LLONG_MAX
,
1027 SetPageReclaim(page
);
1028 res
= mapping
->a_ops
->writepage(page
, &wbc
);
1030 handle_write_error(mapping
, page
, res
);
1031 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
1032 ClearPageReclaim(page
);
1033 return PAGE_ACTIVATE
;
1036 if (!PageWriteback(page
)) {
1037 /* synchronous write or broken a_ops? */
1038 ClearPageReclaim(page
);
1040 trace_mm_vmscan_writepage(page
);
1041 inc_node_page_state(page
, NR_VMSCAN_WRITE
);
1042 return PAGE_SUCCESS
;
1049 * Same as remove_mapping, but if the page is removed from the mapping, it
1050 * gets returned with a refcount of 0.
1052 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
,
1053 bool reclaimed
, struct mem_cgroup
*target_memcg
)
1055 unsigned long flags
;
1057 void *shadow
= NULL
;
1059 BUG_ON(!PageLocked(page
));
1060 BUG_ON(mapping
!= page_mapping(page
));
1062 xa_lock_irqsave(&mapping
->i_pages
, flags
);
1064 * The non racy check for a busy page.
1066 * Must be careful with the order of the tests. When someone has
1067 * a ref to the page, it may be possible that they dirty it then
1068 * drop the reference. So if PageDirty is tested before page_count
1069 * here, then the following race may occur:
1071 * get_user_pages(&page);
1072 * [user mapping goes away]
1074 * !PageDirty(page) [good]
1075 * SetPageDirty(page);
1077 * !page_count(page) [good, discard it]
1079 * [oops, our write_to data is lost]
1081 * Reversing the order of the tests ensures such a situation cannot
1082 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
1083 * load is not satisfied before that of page->_refcount.
1085 * Note that if SetPageDirty is always performed via set_page_dirty,
1086 * and thus under the i_pages lock, then this ordering is not required.
1088 refcount
= 1 + compound_nr(page
);
1089 if (!page_ref_freeze(page
, refcount
))
1091 /* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */
1092 if (unlikely(PageDirty(page
))) {
1093 page_ref_unfreeze(page
, refcount
);
1097 if (PageSwapCache(page
)) {
1098 swp_entry_t swap
= { .val
= page_private(page
) };
1099 mem_cgroup_swapout(page
, swap
);
1100 if (reclaimed
&& !mapping_exiting(mapping
))
1101 shadow
= workingset_eviction(page
, target_memcg
);
1102 __delete_from_swap_cache(page
, swap
, shadow
);
1103 xa_unlock_irqrestore(&mapping
->i_pages
, flags
);
1104 put_swap_page(page
, swap
);
1106 void (*freepage
)(struct page
*);
1108 freepage
= mapping
->a_ops
->freepage
;
1110 * Remember a shadow entry for reclaimed file cache in
1111 * order to detect refaults, thus thrashing, later on.
1113 * But don't store shadows in an address space that is
1114 * already exiting. This is not just an optimization,
1115 * inode reclaim needs to empty out the radix tree or
1116 * the nodes are lost. Don't plant shadows behind its
1119 * We also don't store shadows for DAX mappings because the
1120 * only page cache pages found in these are zero pages
1121 * covering holes, and because we don't want to mix DAX
1122 * exceptional entries and shadow exceptional entries in the
1123 * same address_space.
1125 if (reclaimed
&& page_is_file_lru(page
) &&
1126 !mapping_exiting(mapping
) && !dax_mapping(mapping
))
1127 shadow
= workingset_eviction(page
, target_memcg
);
1128 __delete_from_page_cache(page
, shadow
);
1129 xa_unlock_irqrestore(&mapping
->i_pages
, flags
);
1131 if (freepage
!= NULL
)
1138 xa_unlock_irqrestore(&mapping
->i_pages
, flags
);
1143 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
1144 * someone else has a ref on the page, abort and return 0. If it was
1145 * successfully detached, return 1. Assumes the caller has a single ref on
1148 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
1150 if (__remove_mapping(mapping
, page
, false, NULL
)) {
1152 * Unfreezing the refcount with 1 rather than 2 effectively
1153 * drops the pagecache ref for us without requiring another
1156 page_ref_unfreeze(page
, 1);
1163 * putback_lru_page - put previously isolated page onto appropriate LRU list
1164 * @page: page to be put back to appropriate lru list
1166 * Add previously isolated @page to appropriate LRU list.
1167 * Page may still be unevictable for other reasons.
1169 * lru_lock must not be held, interrupts must be enabled.
1171 void putback_lru_page(struct page
*page
)
1173 lru_cache_add(page
);
1174 put_page(page
); /* drop ref from isolate */
1177 enum page_references
{
1179 PAGEREF_RECLAIM_CLEAN
,
1184 static enum page_references
page_check_references(struct page
*page
,
1185 struct scan_control
*sc
)
1187 int referenced_ptes
, referenced_page
;
1188 unsigned long vm_flags
;
1190 referenced_ptes
= page_referenced(page
, 1, sc
->target_mem_cgroup
,
1192 referenced_page
= TestClearPageReferenced(page
);
1195 * Mlock lost the isolation race with us. Let try_to_unmap()
1196 * move the page to the unevictable list.
1198 if (vm_flags
& VM_LOCKED
)
1199 return PAGEREF_RECLAIM
;
1201 if (referenced_ptes
) {
1203 * All mapped pages start out with page table
1204 * references from the instantiating fault, so we need
1205 * to look twice if a mapped file page is used more
1208 * Mark it and spare it for another trip around the
1209 * inactive list. Another page table reference will
1210 * lead to its activation.
1212 * Note: the mark is set for activated pages as well
1213 * so that recently deactivated but used pages are
1214 * quickly recovered.
1216 SetPageReferenced(page
);
1218 if (referenced_page
|| referenced_ptes
> 1)
1219 return PAGEREF_ACTIVATE
;
1222 * Activate file-backed executable pages after first usage.
1224 if ((vm_flags
& VM_EXEC
) && !PageSwapBacked(page
))
1225 return PAGEREF_ACTIVATE
;
1227 return PAGEREF_KEEP
;
1230 /* Reclaim if clean, defer dirty pages to writeback */
1231 if (referenced_page
&& !PageSwapBacked(page
))
1232 return PAGEREF_RECLAIM_CLEAN
;
1234 return PAGEREF_RECLAIM
;
1237 /* Check if a page is dirty or under writeback */
1238 static void page_check_dirty_writeback(struct page
*page
,
1239 bool *dirty
, bool *writeback
)
1241 struct address_space
*mapping
;
1244 * Anonymous pages are not handled by flushers and must be written
1245 * from reclaim context. Do not stall reclaim based on them
1247 if (!page_is_file_lru(page
) ||
1248 (PageAnon(page
) && !PageSwapBacked(page
))) {
1254 /* By default assume that the page flags are accurate */
1255 *dirty
= PageDirty(page
);
1256 *writeback
= PageWriteback(page
);
1258 /* Verify dirty/writeback state if the filesystem supports it */
1259 if (!page_has_private(page
))
1262 mapping
= page_mapping(page
);
1263 if (mapping
&& mapping
->a_ops
->is_dirty_writeback
)
1264 mapping
->a_ops
->is_dirty_writeback(page
, dirty
, writeback
);
1268 * shrink_page_list() returns the number of reclaimed pages
1270 static unsigned int shrink_page_list(struct list_head
*page_list
,
1271 struct pglist_data
*pgdat
,
1272 struct scan_control
*sc
,
1273 struct reclaim_stat
*stat
,
1274 bool ignore_references
)
1276 LIST_HEAD(ret_pages
);
1277 LIST_HEAD(free_pages
);
1278 unsigned int nr_reclaimed
= 0;
1279 unsigned int pgactivate
= 0;
1281 memset(stat
, 0, sizeof(*stat
));
1284 while (!list_empty(page_list
)) {
1285 struct address_space
*mapping
;
1287 enum page_references references
= PAGEREF_RECLAIM
;
1288 bool dirty
, writeback
, may_enter_fs
;
1289 unsigned int nr_pages
;
1293 page
= lru_to_page(page_list
);
1294 list_del(&page
->lru
);
1296 if (!trylock_page(page
))
1299 VM_BUG_ON_PAGE(PageActive(page
), page
);
1301 nr_pages
= compound_nr(page
);
1303 /* Account the number of base pages even though THP */
1304 sc
->nr_scanned
+= nr_pages
;
1306 if (unlikely(!page_evictable(page
)))
1307 goto activate_locked
;
1309 if (!sc
->may_unmap
&& page_mapped(page
))
1312 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
1313 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
1316 * The number of dirty pages determines if a node is marked
1317 * reclaim_congested which affects wait_iff_congested. kswapd
1318 * will stall and start writing pages if the tail of the LRU
1319 * is all dirty unqueued pages.
1321 page_check_dirty_writeback(page
, &dirty
, &writeback
);
1322 if (dirty
|| writeback
)
1325 if (dirty
&& !writeback
)
1326 stat
->nr_unqueued_dirty
++;
1329 * Treat this page as congested if the underlying BDI is or if
1330 * pages are cycling through the LRU so quickly that the
1331 * pages marked for immediate reclaim are making it to the
1332 * end of the LRU a second time.
1334 mapping
= page_mapping(page
);
1335 if (((dirty
|| writeback
) && mapping
&&
1336 inode_write_congested(mapping
->host
)) ||
1337 (writeback
&& PageReclaim(page
)))
1338 stat
->nr_congested
++;
1341 * If a page at the tail of the LRU is under writeback, there
1342 * are three cases to consider.
1344 * 1) If reclaim is encountering an excessive number of pages
1345 * under writeback and this page is both under writeback and
1346 * PageReclaim then it indicates that pages are being queued
1347 * for IO but are being recycled through the LRU before the
1348 * IO can complete. Waiting on the page itself risks an
1349 * indefinite stall if it is impossible to writeback the
1350 * page due to IO error or disconnected storage so instead
1351 * note that the LRU is being scanned too quickly and the
1352 * caller can stall after page list has been processed.
1354 * 2) Global or new memcg reclaim encounters a page that is
1355 * not marked for immediate reclaim, or the caller does not
1356 * have __GFP_FS (or __GFP_IO if it's simply going to swap,
1357 * not to fs). In this case mark the page for immediate
1358 * reclaim and continue scanning.
1360 * Require may_enter_fs because we would wait on fs, which
1361 * may not have submitted IO yet. And the loop driver might
1362 * enter reclaim, and deadlock if it waits on a page for
1363 * which it is needed to do the write (loop masks off
1364 * __GFP_IO|__GFP_FS for this reason); but more thought
1365 * would probably show more reasons.
1367 * 3) Legacy memcg encounters a page that is already marked
1368 * PageReclaim. memcg does not have any dirty pages
1369 * throttling so we could easily OOM just because too many
1370 * pages are in writeback and there is nothing else to
1371 * reclaim. Wait for the writeback to complete.
1373 * In cases 1) and 2) we activate the pages to get them out of
1374 * the way while we continue scanning for clean pages on the
1375 * inactive list and refilling from the active list. The
1376 * observation here is that waiting for disk writes is more
1377 * expensive than potentially causing reloads down the line.
1378 * Since they're marked for immediate reclaim, they won't put
1379 * memory pressure on the cache working set any longer than it
1380 * takes to write them to disk.
1382 if (PageWriteback(page
)) {
1384 if (current_is_kswapd() &&
1385 PageReclaim(page
) &&
1386 test_bit(PGDAT_WRITEBACK
, &pgdat
->flags
)) {
1387 stat
->nr_immediate
++;
1388 goto activate_locked
;
1391 } else if (writeback_throttling_sane(sc
) ||
1392 !PageReclaim(page
) || !may_enter_fs
) {
1394 * This is slightly racy - end_page_writeback()
1395 * might have just cleared PageReclaim, then
1396 * setting PageReclaim here end up interpreted
1397 * as PageReadahead - but that does not matter
1398 * enough to care. What we do want is for this
1399 * page to have PageReclaim set next time memcg
1400 * reclaim reaches the tests above, so it will
1401 * then wait_on_page_writeback() to avoid OOM;
1402 * and it's also appropriate in global reclaim.
1404 SetPageReclaim(page
);
1405 stat
->nr_writeback
++;
1406 goto activate_locked
;
1411 wait_on_page_writeback(page
);
1412 /* then go back and try same page again */
1413 list_add_tail(&page
->lru
, page_list
);
1418 if (!ignore_references
)
1419 references
= page_check_references(page
, sc
);
1421 switch (references
) {
1422 case PAGEREF_ACTIVATE
:
1423 goto activate_locked
;
1425 stat
->nr_ref_keep
+= nr_pages
;
1427 case PAGEREF_RECLAIM
:
1428 case PAGEREF_RECLAIM_CLEAN
:
1429 ; /* try to reclaim the page below */
1433 * Anonymous process memory has backing store?
1434 * Try to allocate it some swap space here.
1435 * Lazyfree page could be freed directly
1437 if (PageAnon(page
) && PageSwapBacked(page
)) {
1438 if (!PageSwapCache(page
)) {
1439 if (!(sc
->gfp_mask
& __GFP_IO
))
1441 if (page_maybe_dma_pinned(page
))
1443 if (PageTransHuge(page
)) {
1444 /* cannot split THP, skip it */
1445 if (!can_split_huge_page(page
, NULL
))
1446 goto activate_locked
;
1448 * Split pages without a PMD map right
1449 * away. Chances are some or all of the
1450 * tail pages can be freed without IO.
1452 if (!compound_mapcount(page
) &&
1453 split_huge_page_to_list(page
,
1455 goto activate_locked
;
1457 if (!add_to_swap(page
)) {
1458 if (!PageTransHuge(page
))
1459 goto activate_locked_split
;
1460 /* Fallback to swap normal pages */
1461 if (split_huge_page_to_list(page
,
1463 goto activate_locked
;
1464 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1465 count_vm_event(THP_SWPOUT_FALLBACK
);
1467 if (!add_to_swap(page
))
1468 goto activate_locked_split
;
1471 may_enter_fs
= true;
1473 /* Adding to swap updated mapping */
1474 mapping
= page_mapping(page
);
1476 } else if (unlikely(PageTransHuge(page
))) {
1477 /* Split file THP */
1478 if (split_huge_page_to_list(page
, page_list
))
1483 * THP may get split above, need minus tail pages and update
1484 * nr_pages to avoid accounting tail pages twice.
1486 * The tail pages that are added into swap cache successfully
1489 if ((nr_pages
> 1) && !PageTransHuge(page
)) {
1490 sc
->nr_scanned
-= (nr_pages
- 1);
1495 * The page is mapped into the page tables of one or more
1496 * processes. Try to unmap it here.
1498 if (page_mapped(page
)) {
1499 enum ttu_flags flags
= TTU_BATCH_FLUSH
;
1500 bool was_swapbacked
= PageSwapBacked(page
);
1502 if (unlikely(PageTransHuge(page
)))
1503 flags
|= TTU_SPLIT_HUGE_PMD
;
1505 try_to_unmap(page
, flags
);
1506 if (page_mapped(page
)) {
1507 stat
->nr_unmap_fail
+= nr_pages
;
1508 if (!was_swapbacked
&& PageSwapBacked(page
))
1509 stat
->nr_lazyfree_fail
+= nr_pages
;
1510 goto activate_locked
;
1514 if (PageDirty(page
)) {
1516 * Only kswapd can writeback filesystem pages
1517 * to avoid risk of stack overflow. But avoid
1518 * injecting inefficient single-page IO into
1519 * flusher writeback as much as possible: only
1520 * write pages when we've encountered many
1521 * dirty pages, and when we've already scanned
1522 * the rest of the LRU for clean pages and see
1523 * the same dirty pages again (PageReclaim).
1525 if (page_is_file_lru(page
) &&
1526 (!current_is_kswapd() || !PageReclaim(page
) ||
1527 !test_bit(PGDAT_DIRTY
, &pgdat
->flags
))) {
1529 * Immediately reclaim when written back.
1530 * Similar in principal to deactivate_page()
1531 * except we already have the page isolated
1532 * and know it's dirty
1534 inc_node_page_state(page
, NR_VMSCAN_IMMEDIATE
);
1535 SetPageReclaim(page
);
1537 goto activate_locked
;
1540 if (references
== PAGEREF_RECLAIM_CLEAN
)
1544 if (!sc
->may_writepage
)
1548 * Page is dirty. Flush the TLB if a writable entry
1549 * potentially exists to avoid CPU writes after IO
1550 * starts and then write it out here.
1552 try_to_unmap_flush_dirty();
1553 switch (pageout(page
, mapping
)) {
1557 goto activate_locked
;
1559 stat
->nr_pageout
+= thp_nr_pages(page
);
1561 if (PageWriteback(page
))
1563 if (PageDirty(page
))
1567 * A synchronous write - probably a ramdisk. Go
1568 * ahead and try to reclaim the page.
1570 if (!trylock_page(page
))
1572 if (PageDirty(page
) || PageWriteback(page
))
1574 mapping
= page_mapping(page
);
1577 ; /* try to free the page below */
1582 * If the page has buffers, try to free the buffer mappings
1583 * associated with this page. If we succeed we try to free
1586 * We do this even if the page is PageDirty().
1587 * try_to_release_page() does not perform I/O, but it is
1588 * possible for a page to have PageDirty set, but it is actually
1589 * clean (all its buffers are clean). This happens if the
1590 * buffers were written out directly, with submit_bh(). ext3
1591 * will do this, as well as the blockdev mapping.
1592 * try_to_release_page() will discover that cleanness and will
1593 * drop the buffers and mark the page clean - it can be freed.
1595 * Rarely, pages can have buffers and no ->mapping. These are
1596 * the pages which were not successfully invalidated in
1597 * truncate_cleanup_page(). We try to drop those buffers here
1598 * and if that worked, and the page is no longer mapped into
1599 * process address space (page_count == 1) it can be freed.
1600 * Otherwise, leave the page on the LRU so it is swappable.
1602 if (page_has_private(page
)) {
1603 if (!try_to_release_page(page
, sc
->gfp_mask
))
1604 goto activate_locked
;
1605 if (!mapping
&& page_count(page
) == 1) {
1607 if (put_page_testzero(page
))
1611 * rare race with speculative reference.
1612 * the speculative reference will free
1613 * this page shortly, so we may
1614 * increment nr_reclaimed here (and
1615 * leave it off the LRU).
1623 if (PageAnon(page
) && !PageSwapBacked(page
)) {
1624 /* follow __remove_mapping for reference */
1625 if (!page_ref_freeze(page
, 1))
1627 if (PageDirty(page
)) {
1628 page_ref_unfreeze(page
, 1);
1632 count_vm_event(PGLAZYFREED
);
1633 count_memcg_page_event(page
, PGLAZYFREED
);
1634 } else if (!mapping
|| !__remove_mapping(mapping
, page
, true,
1635 sc
->target_mem_cgroup
))
1641 * THP may get swapped out in a whole, need account
1644 nr_reclaimed
+= nr_pages
;
1647 * Is there need to periodically free_page_list? It would
1648 * appear not as the counts should be low
1650 if (unlikely(PageTransHuge(page
)))
1651 destroy_compound_page(page
);
1653 list_add(&page
->lru
, &free_pages
);
1656 activate_locked_split
:
1658 * The tail pages that are failed to add into swap cache
1659 * reach here. Fixup nr_scanned and nr_pages.
1662 sc
->nr_scanned
-= (nr_pages
- 1);
1666 /* Not a candidate for swapping, so reclaim swap space. */
1667 if (PageSwapCache(page
) && (mem_cgroup_swap_full(page
) ||
1669 try_to_free_swap(page
);
1670 VM_BUG_ON_PAGE(PageActive(page
), page
);
1671 if (!PageMlocked(page
)) {
1672 int type
= page_is_file_lru(page
);
1673 SetPageActive(page
);
1674 stat
->nr_activate
[type
] += nr_pages
;
1675 count_memcg_page_event(page
, PGACTIVATE
);
1680 list_add(&page
->lru
, &ret_pages
);
1681 VM_BUG_ON_PAGE(PageLRU(page
) || PageUnevictable(page
), page
);
1684 pgactivate
= stat
->nr_activate
[0] + stat
->nr_activate
[1];
1686 mem_cgroup_uncharge_list(&free_pages
);
1687 try_to_unmap_flush();
1688 free_unref_page_list(&free_pages
);
1690 list_splice(&ret_pages
, page_list
);
1691 count_vm_events(PGACTIVATE
, pgactivate
);
1693 return nr_reclaimed
;
1696 unsigned int reclaim_clean_pages_from_list(struct zone
*zone
,
1697 struct list_head
*page_list
)
1699 struct scan_control sc
= {
1700 .gfp_mask
= GFP_KERNEL
,
1701 .priority
= DEF_PRIORITY
,
1704 struct reclaim_stat stat
;
1705 unsigned int nr_reclaimed
;
1706 struct page
*page
, *next
;
1707 LIST_HEAD(clean_pages
);
1708 unsigned int noreclaim_flag
;
1710 list_for_each_entry_safe(page
, next
, page_list
, lru
) {
1711 if (!PageHuge(page
) && page_is_file_lru(page
) &&
1712 !PageDirty(page
) && !__PageMovable(page
) &&
1713 !PageUnevictable(page
)) {
1714 ClearPageActive(page
);
1715 list_move(&page
->lru
, &clean_pages
);
1720 * We should be safe here since we are only dealing with file pages and
1721 * we are not kswapd and therefore cannot write dirty file pages. But
1722 * call memalloc_noreclaim_save() anyway, just in case these conditions
1723 * change in the future.
1725 noreclaim_flag
= memalloc_noreclaim_save();
1726 nr_reclaimed
= shrink_page_list(&clean_pages
, zone
->zone_pgdat
, &sc
,
1728 memalloc_noreclaim_restore(noreclaim_flag
);
1730 list_splice(&clean_pages
, page_list
);
1731 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_FILE
,
1732 -(long)nr_reclaimed
);
1734 * Since lazyfree pages are isolated from file LRU from the beginning,
1735 * they will rotate back to anonymous LRU in the end if it failed to
1736 * discard so isolated count will be mismatched.
1737 * Compensate the isolated count for both LRU lists.
1739 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_ANON
,
1740 stat
.nr_lazyfree_fail
);
1741 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_FILE
,
1742 -(long)stat
.nr_lazyfree_fail
);
1743 return nr_reclaimed
;
1747 * Attempt to remove the specified page from its LRU. Only take this page
1748 * if it is of the appropriate PageActive status. Pages which are being
1749 * freed elsewhere are also ignored.
1751 * page: page to consider
1752 * mode: one of the LRU isolation modes defined above
1754 * returns true on success, false on failure.
1756 bool __isolate_lru_page_prepare(struct page
*page
, isolate_mode_t mode
)
1758 /* Only take pages on the LRU. */
1762 /* Compaction should not handle unevictable pages but CMA can do so */
1763 if (PageUnevictable(page
) && !(mode
& ISOLATE_UNEVICTABLE
))
1767 * To minimise LRU disruption, the caller can indicate that it only
1768 * wants to isolate pages it will be able to operate on without
1769 * blocking - clean pages for the most part.
1771 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1772 * that it is possible to migrate without blocking
1774 if (mode
& ISOLATE_ASYNC_MIGRATE
) {
1775 /* All the caller can do on PageWriteback is block */
1776 if (PageWriteback(page
))
1779 if (PageDirty(page
)) {
1780 struct address_space
*mapping
;
1784 * Only pages without mappings or that have a
1785 * ->migratepage callback are possible to migrate
1786 * without blocking. However, we can be racing with
1787 * truncation so it's necessary to lock the page
1788 * to stabilise the mapping as truncation holds
1789 * the page lock until after the page is removed
1790 * from the page cache.
1792 if (!trylock_page(page
))
1795 mapping
= page_mapping(page
);
1796 migrate_dirty
= !mapping
|| mapping
->a_ops
->migratepage
;
1803 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1810 * Update LRU sizes after isolating pages. The LRU size updates must
1811 * be complete before mem_cgroup_update_lru_size due to a sanity check.
1813 static __always_inline
void update_lru_sizes(struct lruvec
*lruvec
,
1814 enum lru_list lru
, unsigned long *nr_zone_taken
)
1818 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
1819 if (!nr_zone_taken
[zid
])
1822 update_lru_size(lruvec
, lru
, zid
, -nr_zone_taken
[zid
]);
1828 * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
1830 * lruvec->lru_lock is heavily contended. Some of the functions that
1831 * shrink the lists perform better by taking out a batch of pages
1832 * and working on them outside the LRU lock.
1834 * For pagecache intensive workloads, this function is the hottest
1835 * spot in the kernel (apart from copy_*_user functions).
1837 * Lru_lock must be held before calling this function.
1839 * @nr_to_scan: The number of eligible pages to look through on the list.
1840 * @lruvec: The LRU vector to pull pages from.
1841 * @dst: The temp list to put pages on to.
1842 * @nr_scanned: The number of pages that were scanned.
1843 * @sc: The scan_control struct for this reclaim session
1844 * @lru: LRU list id for isolating
1846 * returns how many pages were moved onto *@dst.
1848 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1849 struct lruvec
*lruvec
, struct list_head
*dst
,
1850 unsigned long *nr_scanned
, struct scan_control
*sc
,
1853 struct list_head
*src
= &lruvec
->lists
[lru
];
1854 unsigned long nr_taken
= 0;
1855 unsigned long nr_zone_taken
[MAX_NR_ZONES
] = { 0 };
1856 unsigned long nr_skipped
[MAX_NR_ZONES
] = { 0, };
1857 unsigned long skipped
= 0;
1858 unsigned long scan
, total_scan
, nr_pages
;
1859 LIST_HEAD(pages_skipped
);
1860 isolate_mode_t mode
= (sc
->may_unmap
? 0 : ISOLATE_UNMAPPED
);
1864 while (scan
< nr_to_scan
&& !list_empty(src
)) {
1867 page
= lru_to_page(src
);
1868 prefetchw_prev_lru_page(page
, src
, flags
);
1870 nr_pages
= compound_nr(page
);
1871 total_scan
+= nr_pages
;
1873 if (page_zonenum(page
) > sc
->reclaim_idx
) {
1874 list_move(&page
->lru
, &pages_skipped
);
1875 nr_skipped
[page_zonenum(page
)] += nr_pages
;
1880 * Do not count skipped pages because that makes the function
1881 * return with no isolated pages if the LRU mostly contains
1882 * ineligible pages. This causes the VM to not reclaim any
1883 * pages, triggering a premature OOM.
1885 * Account all tail pages of THP. This would not cause
1886 * premature OOM since __isolate_lru_page() returns -EBUSY
1887 * only when the page is being freed somewhere else.
1890 if (!__isolate_lru_page_prepare(page
, mode
)) {
1891 /* It is being freed elsewhere */
1892 list_move(&page
->lru
, src
);
1896 * Be careful not to clear PageLRU until after we're
1897 * sure the page is not being freed elsewhere -- the
1898 * page release code relies on it.
1900 if (unlikely(!get_page_unless_zero(page
))) {
1901 list_move(&page
->lru
, src
);
1905 if (!TestClearPageLRU(page
)) {
1906 /* Another thread is already isolating this page */
1908 list_move(&page
->lru
, src
);
1912 nr_taken
+= nr_pages
;
1913 nr_zone_taken
[page_zonenum(page
)] += nr_pages
;
1914 list_move(&page
->lru
, dst
);
1918 * Splice any skipped pages to the start of the LRU list. Note that
1919 * this disrupts the LRU order when reclaiming for lower zones but
1920 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
1921 * scanning would soon rescan the same pages to skip and put the
1922 * system at risk of premature OOM.
1924 if (!list_empty(&pages_skipped
)) {
1927 list_splice(&pages_skipped
, src
);
1928 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
1929 if (!nr_skipped
[zid
])
1932 __count_zid_vm_events(PGSCAN_SKIP
, zid
, nr_skipped
[zid
]);
1933 skipped
+= nr_skipped
[zid
];
1936 *nr_scanned
= total_scan
;
1937 trace_mm_vmscan_lru_isolate(sc
->reclaim_idx
, sc
->order
, nr_to_scan
,
1938 total_scan
, skipped
, nr_taken
, mode
, lru
);
1939 update_lru_sizes(lruvec
, lru
, nr_zone_taken
);
1944 * isolate_lru_page - tries to isolate a page from its LRU list
1945 * @page: page to isolate from its LRU list
1947 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1948 * vmstat statistic corresponding to whatever LRU list the page was on.
1950 * Returns 0 if the page was removed from an LRU list.
1951 * Returns -EBUSY if the page was not on an LRU list.
1953 * The returned page will have PageLRU() cleared. If it was found on
1954 * the active list, it will have PageActive set. If it was found on
1955 * the unevictable list, it will have the PageUnevictable bit set. That flag
1956 * may need to be cleared by the caller before letting the page go.
1958 * The vmstat statistic corresponding to the list on which the page was
1959 * found will be decremented.
1963 * (1) Must be called with an elevated refcount on the page. This is a
1964 * fundamental difference from isolate_lru_pages (which is called
1965 * without a stable reference).
1966 * (2) the lru_lock must not be held.
1967 * (3) interrupts must be enabled.
1969 int isolate_lru_page(struct page
*page
)
1973 VM_BUG_ON_PAGE(!page_count(page
), page
);
1974 WARN_RATELIMIT(PageTail(page
), "trying to isolate tail page");
1976 if (TestClearPageLRU(page
)) {
1977 struct lruvec
*lruvec
;
1980 lruvec
= lock_page_lruvec_irq(page
);
1981 del_page_from_lru_list(page
, lruvec
);
1982 unlock_page_lruvec_irq(lruvec
);
1990 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1991 * then get rescheduled. When there are massive number of tasks doing page
1992 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1993 * the LRU list will go small and be scanned faster than necessary, leading to
1994 * unnecessary swapping, thrashing and OOM.
1996 static int too_many_isolated(struct pglist_data
*pgdat
, int file
,
1997 struct scan_control
*sc
)
1999 unsigned long inactive
, isolated
;
2001 if (current_is_kswapd())
2004 if (!writeback_throttling_sane(sc
))
2008 inactive
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
2009 isolated
= node_page_state(pgdat
, NR_ISOLATED_FILE
);
2011 inactive
= node_page_state(pgdat
, NR_INACTIVE_ANON
);
2012 isolated
= node_page_state(pgdat
, NR_ISOLATED_ANON
);
2016 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
2017 * won't get blocked by normal direct-reclaimers, forming a circular
2020 if ((sc
->gfp_mask
& (__GFP_IO
| __GFP_FS
)) == (__GFP_IO
| __GFP_FS
))
2023 return isolated
> inactive
;
2027 * move_pages_to_lru() moves pages from private @list to appropriate LRU list.
2028 * On return, @list is reused as a list of pages to be freed by the caller.
2030 * Returns the number of pages moved to the given lruvec.
2032 static unsigned int move_pages_to_lru(struct lruvec
*lruvec
,
2033 struct list_head
*list
)
2035 int nr_pages
, nr_moved
= 0;
2036 LIST_HEAD(pages_to_free
);
2039 while (!list_empty(list
)) {
2040 page
= lru_to_page(list
);
2041 VM_BUG_ON_PAGE(PageLRU(page
), page
);
2042 list_del(&page
->lru
);
2043 if (unlikely(!page_evictable(page
))) {
2044 spin_unlock_irq(&lruvec
->lru_lock
);
2045 putback_lru_page(page
);
2046 spin_lock_irq(&lruvec
->lru_lock
);
2051 * The SetPageLRU needs to be kept here for list integrity.
2053 * #0 move_pages_to_lru #1 release_pages
2054 * if !put_page_testzero
2055 * if (put_page_testzero())
2056 * !PageLRU //skip lru_lock
2058 * list_add(&page->lru,)
2059 * list_add(&page->lru,)
2063 if (unlikely(put_page_testzero(page
))) {
2064 __clear_page_lru_flags(page
);
2066 if (unlikely(PageCompound(page
))) {
2067 spin_unlock_irq(&lruvec
->lru_lock
);
2068 destroy_compound_page(page
);
2069 spin_lock_irq(&lruvec
->lru_lock
);
2071 list_add(&page
->lru
, &pages_to_free
);
2077 * All pages were isolated from the same lruvec (and isolation
2078 * inhibits memcg migration).
2080 VM_BUG_ON_PAGE(!page_matches_lruvec(page
, lruvec
), page
);
2081 add_page_to_lru_list(page
, lruvec
);
2082 nr_pages
= thp_nr_pages(page
);
2083 nr_moved
+= nr_pages
;
2084 if (PageActive(page
))
2085 workingset_age_nonresident(lruvec
, nr_pages
);
2089 * To save our caller's stack, now use input list for pages to free.
2091 list_splice(&pages_to_free
, list
);
2097 * If a kernel thread (such as nfsd for loop-back mounts) services
2098 * a backing device by writing to the page cache it sets PF_LOCAL_THROTTLE.
2099 * In that case we should only throttle if the backing device it is
2100 * writing to is congested. In other cases it is safe to throttle.
2102 static int current_may_throttle(void)
2104 return !(current
->flags
& PF_LOCAL_THROTTLE
) ||
2105 current
->backing_dev_info
== NULL
||
2106 bdi_write_congested(current
->backing_dev_info
);
2110 * shrink_inactive_list() is a helper for shrink_node(). It returns the number
2111 * of reclaimed pages
2113 static unsigned long
2114 shrink_inactive_list(unsigned long nr_to_scan
, struct lruvec
*lruvec
,
2115 struct scan_control
*sc
, enum lru_list lru
)
2117 LIST_HEAD(page_list
);
2118 unsigned long nr_scanned
;
2119 unsigned int nr_reclaimed
= 0;
2120 unsigned long nr_taken
;
2121 struct reclaim_stat stat
;
2122 bool file
= is_file_lru(lru
);
2123 enum vm_event_item item
;
2124 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2125 bool stalled
= false;
2127 while (unlikely(too_many_isolated(pgdat
, file
, sc
))) {
2131 /* wait a bit for the reclaimer. */
2135 /* We are about to die and free our memory. Return now. */
2136 if (fatal_signal_pending(current
))
2137 return SWAP_CLUSTER_MAX
;
2142 spin_lock_irq(&lruvec
->lru_lock
);
2144 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &page_list
,
2145 &nr_scanned
, sc
, lru
);
2147 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
2148 item
= current_is_kswapd() ? PGSCAN_KSWAPD
: PGSCAN_DIRECT
;
2149 if (!cgroup_reclaim(sc
))
2150 __count_vm_events(item
, nr_scanned
);
2151 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_scanned
);
2152 __count_vm_events(PGSCAN_ANON
+ file
, nr_scanned
);
2154 spin_unlock_irq(&lruvec
->lru_lock
);
2159 nr_reclaimed
= shrink_page_list(&page_list
, pgdat
, sc
, &stat
, false);
2161 spin_lock_irq(&lruvec
->lru_lock
);
2162 move_pages_to_lru(lruvec
, &page_list
);
2164 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2165 item
= current_is_kswapd() ? PGSTEAL_KSWAPD
: PGSTEAL_DIRECT
;
2166 if (!cgroup_reclaim(sc
))
2167 __count_vm_events(item
, nr_reclaimed
);
2168 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_reclaimed
);
2169 __count_vm_events(PGSTEAL_ANON
+ file
, nr_reclaimed
);
2170 spin_unlock_irq(&lruvec
->lru_lock
);
2172 lru_note_cost(lruvec
, file
, stat
.nr_pageout
);
2173 mem_cgroup_uncharge_list(&page_list
);
2174 free_unref_page_list(&page_list
);
2177 * If dirty pages are scanned that are not queued for IO, it
2178 * implies that flushers are not doing their job. This can
2179 * happen when memory pressure pushes dirty pages to the end of
2180 * the LRU before the dirty limits are breached and the dirty
2181 * data has expired. It can also happen when the proportion of
2182 * dirty pages grows not through writes but through memory
2183 * pressure reclaiming all the clean cache. And in some cases,
2184 * the flushers simply cannot keep up with the allocation
2185 * rate. Nudge the flusher threads in case they are asleep.
2187 if (stat
.nr_unqueued_dirty
== nr_taken
)
2188 wakeup_flusher_threads(WB_REASON_VMSCAN
);
2190 sc
->nr
.dirty
+= stat
.nr_dirty
;
2191 sc
->nr
.congested
+= stat
.nr_congested
;
2192 sc
->nr
.unqueued_dirty
+= stat
.nr_unqueued_dirty
;
2193 sc
->nr
.writeback
+= stat
.nr_writeback
;
2194 sc
->nr
.immediate
+= stat
.nr_immediate
;
2195 sc
->nr
.taken
+= nr_taken
;
2197 sc
->nr
.file_taken
+= nr_taken
;
2199 trace_mm_vmscan_lru_shrink_inactive(pgdat
->node_id
,
2200 nr_scanned
, nr_reclaimed
, &stat
, sc
->priority
, file
);
2201 return nr_reclaimed
;
2205 * shrink_active_list() moves pages from the active LRU to the inactive LRU.
2207 * We move them the other way if the page is referenced by one or more
2210 * If the pages are mostly unmapped, the processing is fast and it is
2211 * appropriate to hold lru_lock across the whole operation. But if
2212 * the pages are mapped, the processing is slow (page_referenced()), so
2213 * we should drop lru_lock around each page. It's impossible to balance
2214 * this, so instead we remove the pages from the LRU while processing them.
2215 * It is safe to rely on PG_active against the non-LRU pages in here because
2216 * nobody will play with that bit on a non-LRU page.
2218 * The downside is that we have to touch page->_refcount against each page.
2219 * But we had to alter page->flags anyway.
2221 static void shrink_active_list(unsigned long nr_to_scan
,
2222 struct lruvec
*lruvec
,
2223 struct scan_control
*sc
,
2226 unsigned long nr_taken
;
2227 unsigned long nr_scanned
;
2228 unsigned long vm_flags
;
2229 LIST_HEAD(l_hold
); /* The pages which were snipped off */
2230 LIST_HEAD(l_active
);
2231 LIST_HEAD(l_inactive
);
2233 unsigned nr_deactivate
, nr_activate
;
2234 unsigned nr_rotated
= 0;
2235 int file
= is_file_lru(lru
);
2236 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2240 spin_lock_irq(&lruvec
->lru_lock
);
2242 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &l_hold
,
2243 &nr_scanned
, sc
, lru
);
2245 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
2247 if (!cgroup_reclaim(sc
))
2248 __count_vm_events(PGREFILL
, nr_scanned
);
2249 __count_memcg_events(lruvec_memcg(lruvec
), PGREFILL
, nr_scanned
);
2251 spin_unlock_irq(&lruvec
->lru_lock
);
2253 while (!list_empty(&l_hold
)) {
2255 page
= lru_to_page(&l_hold
);
2256 list_del(&page
->lru
);
2258 if (unlikely(!page_evictable(page
))) {
2259 putback_lru_page(page
);
2263 if (unlikely(buffer_heads_over_limit
)) {
2264 if (page_has_private(page
) && trylock_page(page
)) {
2265 if (page_has_private(page
))
2266 try_to_release_page(page
, 0);
2271 if (page_referenced(page
, 0, sc
->target_mem_cgroup
,
2274 * Identify referenced, file-backed active pages and
2275 * give them one more trip around the active list. So
2276 * that executable code get better chances to stay in
2277 * memory under moderate memory pressure. Anon pages
2278 * are not likely to be evicted by use-once streaming
2279 * IO, plus JVM can create lots of anon VM_EXEC pages,
2280 * so we ignore them here.
2282 if ((vm_flags
& VM_EXEC
) && page_is_file_lru(page
)) {
2283 nr_rotated
+= thp_nr_pages(page
);
2284 list_add(&page
->lru
, &l_active
);
2289 ClearPageActive(page
); /* we are de-activating */
2290 SetPageWorkingset(page
);
2291 list_add(&page
->lru
, &l_inactive
);
2295 * Move pages back to the lru list.
2297 spin_lock_irq(&lruvec
->lru_lock
);
2299 nr_activate
= move_pages_to_lru(lruvec
, &l_active
);
2300 nr_deactivate
= move_pages_to_lru(lruvec
, &l_inactive
);
2301 /* Keep all free pages in l_active list */
2302 list_splice(&l_inactive
, &l_active
);
2304 __count_vm_events(PGDEACTIVATE
, nr_deactivate
);
2305 __count_memcg_events(lruvec_memcg(lruvec
), PGDEACTIVATE
, nr_deactivate
);
2307 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2308 spin_unlock_irq(&lruvec
->lru_lock
);
2310 mem_cgroup_uncharge_list(&l_active
);
2311 free_unref_page_list(&l_active
);
2312 trace_mm_vmscan_lru_shrink_active(pgdat
->node_id
, nr_taken
, nr_activate
,
2313 nr_deactivate
, nr_rotated
, sc
->priority
, file
);
2316 unsigned long reclaim_pages(struct list_head
*page_list
)
2318 int nid
= NUMA_NO_NODE
;
2319 unsigned int nr_reclaimed
= 0;
2320 LIST_HEAD(node_page_list
);
2321 struct reclaim_stat dummy_stat
;
2323 unsigned int noreclaim_flag
;
2324 struct scan_control sc
= {
2325 .gfp_mask
= GFP_KERNEL
,
2326 .priority
= DEF_PRIORITY
,
2332 noreclaim_flag
= memalloc_noreclaim_save();
2334 while (!list_empty(page_list
)) {
2335 page
= lru_to_page(page_list
);
2336 if (nid
== NUMA_NO_NODE
) {
2337 nid
= page_to_nid(page
);
2338 INIT_LIST_HEAD(&node_page_list
);
2341 if (nid
== page_to_nid(page
)) {
2342 ClearPageActive(page
);
2343 list_move(&page
->lru
, &node_page_list
);
2347 nr_reclaimed
+= shrink_page_list(&node_page_list
,
2349 &sc
, &dummy_stat
, false);
2350 while (!list_empty(&node_page_list
)) {
2351 page
= lru_to_page(&node_page_list
);
2352 list_del(&page
->lru
);
2353 putback_lru_page(page
);
2359 if (!list_empty(&node_page_list
)) {
2360 nr_reclaimed
+= shrink_page_list(&node_page_list
,
2362 &sc
, &dummy_stat
, false);
2363 while (!list_empty(&node_page_list
)) {
2364 page
= lru_to_page(&node_page_list
);
2365 list_del(&page
->lru
);
2366 putback_lru_page(page
);
2370 memalloc_noreclaim_restore(noreclaim_flag
);
2372 return nr_reclaimed
;
2375 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
2376 struct lruvec
*lruvec
, struct scan_control
*sc
)
2378 if (is_active_lru(lru
)) {
2379 if (sc
->may_deactivate
& (1 << is_file_lru(lru
)))
2380 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
2382 sc
->skipped_deactivate
= 1;
2386 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
2390 * The inactive anon list should be small enough that the VM never has
2391 * to do too much work.
2393 * The inactive file list should be small enough to leave most memory
2394 * to the established workingset on the scan-resistant active list,
2395 * but large enough to avoid thrashing the aggregate readahead window.
2397 * Both inactive lists should also be large enough that each inactive
2398 * page has a chance to be referenced again before it is reclaimed.
2400 * If that fails and refaulting is observed, the inactive list grows.
2402 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages
2403 * on this LRU, maintained by the pageout code. An inactive_ratio
2404 * of 3 means 3:1 or 25% of the pages are kept on the inactive list.
2407 * memory ratio inactive
2408 * -------------------------------------
2417 static bool inactive_is_low(struct lruvec
*lruvec
, enum lru_list inactive_lru
)
2419 enum lru_list active_lru
= inactive_lru
+ LRU_ACTIVE
;
2420 unsigned long inactive
, active
;
2421 unsigned long inactive_ratio
;
2424 inactive
= lruvec_page_state(lruvec
, NR_LRU_BASE
+ inactive_lru
);
2425 active
= lruvec_page_state(lruvec
, NR_LRU_BASE
+ active_lru
);
2427 gb
= (inactive
+ active
) >> (30 - PAGE_SHIFT
);
2429 inactive_ratio
= int_sqrt(10 * gb
);
2433 return inactive
* inactive_ratio
< active
;
2444 * Determine how aggressively the anon and file LRU lists should be
2445 * scanned. The relative value of each set of LRU lists is determined
2446 * by looking at the fraction of the pages scanned we did rotate back
2447 * onto the active list instead of evict.
2449 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
2450 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
2452 static void get_scan_count(struct lruvec
*lruvec
, struct scan_control
*sc
,
2455 struct mem_cgroup
*memcg
= lruvec_memcg(lruvec
);
2456 unsigned long anon_cost
, file_cost
, total_cost
;
2457 int swappiness
= mem_cgroup_swappiness(memcg
);
2458 u64 fraction
[ANON_AND_FILE
];
2459 u64 denominator
= 0; /* gcc */
2460 enum scan_balance scan_balance
;
2461 unsigned long ap
, fp
;
2464 /* If we have no swap space, do not bother scanning anon pages. */
2465 if (!sc
->may_swap
|| mem_cgroup_get_nr_swap_pages(memcg
) <= 0) {
2466 scan_balance
= SCAN_FILE
;
2471 * Global reclaim will swap to prevent OOM even with no
2472 * swappiness, but memcg users want to use this knob to
2473 * disable swapping for individual groups completely when
2474 * using the memory controller's swap limit feature would be
2477 if (cgroup_reclaim(sc
) && !swappiness
) {
2478 scan_balance
= SCAN_FILE
;
2483 * Do not apply any pressure balancing cleverness when the
2484 * system is close to OOM, scan both anon and file equally
2485 * (unless the swappiness setting disagrees with swapping).
2487 if (!sc
->priority
&& swappiness
) {
2488 scan_balance
= SCAN_EQUAL
;
2493 * If the system is almost out of file pages, force-scan anon.
2495 if (sc
->file_is_tiny
) {
2496 scan_balance
= SCAN_ANON
;
2501 * If there is enough inactive page cache, we do not reclaim
2502 * anything from the anonymous working right now.
2504 if (sc
->cache_trim_mode
) {
2505 scan_balance
= SCAN_FILE
;
2509 scan_balance
= SCAN_FRACT
;
2511 * Calculate the pressure balance between anon and file pages.
2513 * The amount of pressure we put on each LRU is inversely
2514 * proportional to the cost of reclaiming each list, as
2515 * determined by the share of pages that are refaulting, times
2516 * the relative IO cost of bringing back a swapped out
2517 * anonymous page vs reloading a filesystem page (swappiness).
2519 * Although we limit that influence to ensure no list gets
2520 * left behind completely: at least a third of the pressure is
2521 * applied, before swappiness.
2523 * With swappiness at 100, anon and file have equal IO cost.
2525 total_cost
= sc
->anon_cost
+ sc
->file_cost
;
2526 anon_cost
= total_cost
+ sc
->anon_cost
;
2527 file_cost
= total_cost
+ sc
->file_cost
;
2528 total_cost
= anon_cost
+ file_cost
;
2530 ap
= swappiness
* (total_cost
+ 1);
2531 ap
/= anon_cost
+ 1;
2533 fp
= (200 - swappiness
) * (total_cost
+ 1);
2534 fp
/= file_cost
+ 1;
2538 denominator
= ap
+ fp
;
2540 for_each_evictable_lru(lru
) {
2541 int file
= is_file_lru(lru
);
2542 unsigned long lruvec_size
;
2543 unsigned long low
, min
;
2546 lruvec_size
= lruvec_lru_size(lruvec
, lru
, sc
->reclaim_idx
);
2547 mem_cgroup_protection(sc
->target_mem_cgroup
, memcg
,
2552 * Scale a cgroup's reclaim pressure by proportioning
2553 * its current usage to its memory.low or memory.min
2556 * This is important, as otherwise scanning aggression
2557 * becomes extremely binary -- from nothing as we
2558 * approach the memory protection threshold, to totally
2559 * nominal as we exceed it. This results in requiring
2560 * setting extremely liberal protection thresholds. It
2561 * also means we simply get no protection at all if we
2562 * set it too low, which is not ideal.
2564 * If there is any protection in place, we reduce scan
2565 * pressure by how much of the total memory used is
2566 * within protection thresholds.
2568 * There is one special case: in the first reclaim pass,
2569 * we skip over all groups that are within their low
2570 * protection. If that fails to reclaim enough pages to
2571 * satisfy the reclaim goal, we come back and override
2572 * the best-effort low protection. However, we still
2573 * ideally want to honor how well-behaved groups are in
2574 * that case instead of simply punishing them all
2575 * equally. As such, we reclaim them based on how much
2576 * memory they are using, reducing the scan pressure
2577 * again by how much of the total memory used is under
2580 unsigned long cgroup_size
= mem_cgroup_size(memcg
);
2581 unsigned long protection
;
2583 /* memory.low scaling, make sure we retry before OOM */
2584 if (!sc
->memcg_low_reclaim
&& low
> min
) {
2586 sc
->memcg_low_skipped
= 1;
2591 /* Avoid TOCTOU with earlier protection check */
2592 cgroup_size
= max(cgroup_size
, protection
);
2594 scan
= lruvec_size
- lruvec_size
* protection
/
2598 * Minimally target SWAP_CLUSTER_MAX pages to keep
2599 * reclaim moving forwards, avoiding decrementing
2600 * sc->priority further than desirable.
2602 scan
= max(scan
, SWAP_CLUSTER_MAX
);
2607 scan
>>= sc
->priority
;
2610 * If the cgroup's already been deleted, make sure to
2611 * scrape out the remaining cache.
2613 if (!scan
&& !mem_cgroup_online(memcg
))
2614 scan
= min(lruvec_size
, SWAP_CLUSTER_MAX
);
2616 switch (scan_balance
) {
2618 /* Scan lists relative to size */
2622 * Scan types proportional to swappiness and
2623 * their relative recent reclaim efficiency.
2624 * Make sure we don't miss the last page on
2625 * the offlined memory cgroups because of a
2628 scan
= mem_cgroup_online(memcg
) ?
2629 div64_u64(scan
* fraction
[file
], denominator
) :
2630 DIV64_U64_ROUND_UP(scan
* fraction
[file
],
2635 /* Scan one type exclusively */
2636 if ((scan_balance
== SCAN_FILE
) != file
)
2640 /* Look ma, no brain */
2648 static void shrink_lruvec(struct lruvec
*lruvec
, struct scan_control
*sc
)
2650 unsigned long nr
[NR_LRU_LISTS
];
2651 unsigned long targets
[NR_LRU_LISTS
];
2652 unsigned long nr_to_scan
;
2654 unsigned long nr_reclaimed
= 0;
2655 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2656 struct blk_plug plug
;
2659 get_scan_count(lruvec
, sc
, nr
);
2661 /* Record the original scan target for proportional adjustments later */
2662 memcpy(targets
, nr
, sizeof(nr
));
2665 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
2666 * event that can occur when there is little memory pressure e.g.
2667 * multiple streaming readers/writers. Hence, we do not abort scanning
2668 * when the requested number of pages are reclaimed when scanning at
2669 * DEF_PRIORITY on the assumption that the fact we are direct
2670 * reclaiming implies that kswapd is not keeping up and it is best to
2671 * do a batch of work at once. For memcg reclaim one check is made to
2672 * abort proportional reclaim if either the file or anon lru has already
2673 * dropped to zero at the first pass.
2675 scan_adjusted
= (!cgroup_reclaim(sc
) && !current_is_kswapd() &&
2676 sc
->priority
== DEF_PRIORITY
);
2678 blk_start_plug(&plug
);
2679 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2680 nr
[LRU_INACTIVE_FILE
]) {
2681 unsigned long nr_anon
, nr_file
, percentage
;
2682 unsigned long nr_scanned
;
2684 for_each_evictable_lru(lru
) {
2686 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
2687 nr
[lru
] -= nr_to_scan
;
2689 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
2696 if (nr_reclaimed
< nr_to_reclaim
|| scan_adjusted
)
2700 * For kswapd and memcg, reclaim at least the number of pages
2701 * requested. Ensure that the anon and file LRUs are scanned
2702 * proportionally what was requested by get_scan_count(). We
2703 * stop reclaiming one LRU and reduce the amount scanning
2704 * proportional to the original scan target.
2706 nr_file
= nr
[LRU_INACTIVE_FILE
] + nr
[LRU_ACTIVE_FILE
];
2707 nr_anon
= nr
[LRU_INACTIVE_ANON
] + nr
[LRU_ACTIVE_ANON
];
2710 * It's just vindictive to attack the larger once the smaller
2711 * has gone to zero. And given the way we stop scanning the
2712 * smaller below, this makes sure that we only make one nudge
2713 * towards proportionality once we've got nr_to_reclaim.
2715 if (!nr_file
|| !nr_anon
)
2718 if (nr_file
> nr_anon
) {
2719 unsigned long scan_target
= targets
[LRU_INACTIVE_ANON
] +
2720 targets
[LRU_ACTIVE_ANON
] + 1;
2722 percentage
= nr_anon
* 100 / scan_target
;
2724 unsigned long scan_target
= targets
[LRU_INACTIVE_FILE
] +
2725 targets
[LRU_ACTIVE_FILE
] + 1;
2727 percentage
= nr_file
* 100 / scan_target
;
2730 /* Stop scanning the smaller of the LRU */
2732 nr
[lru
+ LRU_ACTIVE
] = 0;
2735 * Recalculate the other LRU scan count based on its original
2736 * scan target and the percentage scanning already complete
2738 lru
= (lru
== LRU_FILE
) ? LRU_BASE
: LRU_FILE
;
2739 nr_scanned
= targets
[lru
] - nr
[lru
];
2740 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2741 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2744 nr_scanned
= targets
[lru
] - nr
[lru
];
2745 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2746 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2748 scan_adjusted
= true;
2750 blk_finish_plug(&plug
);
2751 sc
->nr_reclaimed
+= nr_reclaimed
;
2754 * Even if we did not try to evict anon pages at all, we want to
2755 * rebalance the anon lru active/inactive ratio.
2757 if (total_swap_pages
&& inactive_is_low(lruvec
, LRU_INACTIVE_ANON
))
2758 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2759 sc
, LRU_ACTIVE_ANON
);
2762 /* Use reclaim/compaction for costly allocs or under memory pressure */
2763 static bool in_reclaim_compaction(struct scan_control
*sc
)
2765 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
2766 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
2767 sc
->priority
< DEF_PRIORITY
- 2))
2774 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2775 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2776 * true if more pages should be reclaimed such that when the page allocator
2777 * calls try_to_compact_pages() that it will have enough free pages to succeed.
2778 * It will give up earlier than that if there is difficulty reclaiming pages.
2780 static inline bool should_continue_reclaim(struct pglist_data
*pgdat
,
2781 unsigned long nr_reclaimed
,
2782 struct scan_control
*sc
)
2784 unsigned long pages_for_compaction
;
2785 unsigned long inactive_lru_pages
;
2788 /* If not in reclaim/compaction mode, stop */
2789 if (!in_reclaim_compaction(sc
))
2793 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
2794 * number of pages that were scanned. This will return to the caller
2795 * with the risk reclaim/compaction and the resulting allocation attempt
2796 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
2797 * allocations through requiring that the full LRU list has been scanned
2798 * first, by assuming that zero delta of sc->nr_scanned means full LRU
2799 * scan, but that approximation was wrong, and there were corner cases
2800 * where always a non-zero amount of pages were scanned.
2805 /* If compaction would go ahead or the allocation would succeed, stop */
2806 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
2807 struct zone
*zone
= &pgdat
->node_zones
[z
];
2808 if (!managed_zone(zone
))
2811 switch (compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
)) {
2812 case COMPACT_SUCCESS
:
2813 case COMPACT_CONTINUE
:
2816 /* check next zone */
2822 * If we have not reclaimed enough pages for compaction and the
2823 * inactive lists are large enough, continue reclaiming
2825 pages_for_compaction
= compact_gap(sc
->order
);
2826 inactive_lru_pages
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
2827 if (get_nr_swap_pages() > 0)
2828 inactive_lru_pages
+= node_page_state(pgdat
, NR_INACTIVE_ANON
);
2830 return inactive_lru_pages
> pages_for_compaction
;
2833 static void shrink_node_memcgs(pg_data_t
*pgdat
, struct scan_control
*sc
)
2835 struct mem_cgroup
*target_memcg
= sc
->target_mem_cgroup
;
2836 struct mem_cgroup
*memcg
;
2838 memcg
= mem_cgroup_iter(target_memcg
, NULL
, NULL
);
2840 struct lruvec
*lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
2841 unsigned long reclaimed
;
2842 unsigned long scanned
;
2845 * This loop can become CPU-bound when target memcgs
2846 * aren't eligible for reclaim - either because they
2847 * don't have any reclaimable pages, or because their
2848 * memory is explicitly protected. Avoid soft lockups.
2852 mem_cgroup_calculate_protection(target_memcg
, memcg
);
2854 if (mem_cgroup_below_min(memcg
)) {
2857 * If there is no reclaimable memory, OOM.
2860 } else if (mem_cgroup_below_low(memcg
)) {
2863 * Respect the protection only as long as
2864 * there is an unprotected supply
2865 * of reclaimable memory from other cgroups.
2867 if (!sc
->memcg_low_reclaim
) {
2868 sc
->memcg_low_skipped
= 1;
2871 memcg_memory_event(memcg
, MEMCG_LOW
);
2874 reclaimed
= sc
->nr_reclaimed
;
2875 scanned
= sc
->nr_scanned
;
2877 shrink_lruvec(lruvec
, sc
);
2879 shrink_slab(sc
->gfp_mask
, pgdat
->node_id
, memcg
,
2882 /* Record the group's reclaim efficiency */
2883 vmpressure(sc
->gfp_mask
, memcg
, false,
2884 sc
->nr_scanned
- scanned
,
2885 sc
->nr_reclaimed
- reclaimed
);
2887 } while ((memcg
= mem_cgroup_iter(target_memcg
, memcg
, NULL
)));
2890 static void shrink_node(pg_data_t
*pgdat
, struct scan_control
*sc
)
2892 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2893 unsigned long nr_reclaimed
, nr_scanned
;
2894 struct lruvec
*target_lruvec
;
2895 bool reclaimable
= false;
2898 target_lruvec
= mem_cgroup_lruvec(sc
->target_mem_cgroup
, pgdat
);
2901 memset(&sc
->nr
, 0, sizeof(sc
->nr
));
2903 nr_reclaimed
= sc
->nr_reclaimed
;
2904 nr_scanned
= sc
->nr_scanned
;
2907 * Determine the scan balance between anon and file LRUs.
2909 spin_lock_irq(&target_lruvec
->lru_lock
);
2910 sc
->anon_cost
= target_lruvec
->anon_cost
;
2911 sc
->file_cost
= target_lruvec
->file_cost
;
2912 spin_unlock_irq(&target_lruvec
->lru_lock
);
2915 * Target desirable inactive:active list ratios for the anon
2916 * and file LRU lists.
2918 if (!sc
->force_deactivate
) {
2919 unsigned long refaults
;
2921 refaults
= lruvec_page_state(target_lruvec
,
2922 WORKINGSET_ACTIVATE_ANON
);
2923 if (refaults
!= target_lruvec
->refaults
[0] ||
2924 inactive_is_low(target_lruvec
, LRU_INACTIVE_ANON
))
2925 sc
->may_deactivate
|= DEACTIVATE_ANON
;
2927 sc
->may_deactivate
&= ~DEACTIVATE_ANON
;
2930 * When refaults are being observed, it means a new
2931 * workingset is being established. Deactivate to get
2932 * rid of any stale active pages quickly.
2934 refaults
= lruvec_page_state(target_lruvec
,
2935 WORKINGSET_ACTIVATE_FILE
);
2936 if (refaults
!= target_lruvec
->refaults
[1] ||
2937 inactive_is_low(target_lruvec
, LRU_INACTIVE_FILE
))
2938 sc
->may_deactivate
|= DEACTIVATE_FILE
;
2940 sc
->may_deactivate
&= ~DEACTIVATE_FILE
;
2942 sc
->may_deactivate
= DEACTIVATE_ANON
| DEACTIVATE_FILE
;
2945 * If we have plenty of inactive file pages that aren't
2946 * thrashing, try to reclaim those first before touching
2949 file
= lruvec_page_state(target_lruvec
, NR_INACTIVE_FILE
);
2950 if (file
>> sc
->priority
&& !(sc
->may_deactivate
& DEACTIVATE_FILE
))
2951 sc
->cache_trim_mode
= 1;
2953 sc
->cache_trim_mode
= 0;
2956 * Prevent the reclaimer from falling into the cache trap: as
2957 * cache pages start out inactive, every cache fault will tip
2958 * the scan balance towards the file LRU. And as the file LRU
2959 * shrinks, so does the window for rotation from references.
2960 * This means we have a runaway feedback loop where a tiny
2961 * thrashing file LRU becomes infinitely more attractive than
2962 * anon pages. Try to detect this based on file LRU size.
2964 if (!cgroup_reclaim(sc
)) {
2965 unsigned long total_high_wmark
= 0;
2966 unsigned long free
, anon
;
2969 free
= sum_zone_node_page_state(pgdat
->node_id
, NR_FREE_PAGES
);
2970 file
= node_page_state(pgdat
, NR_ACTIVE_FILE
) +
2971 node_page_state(pgdat
, NR_INACTIVE_FILE
);
2973 for (z
= 0; z
< MAX_NR_ZONES
; z
++) {
2974 struct zone
*zone
= &pgdat
->node_zones
[z
];
2975 if (!managed_zone(zone
))
2978 total_high_wmark
+= high_wmark_pages(zone
);
2982 * Consider anon: if that's low too, this isn't a
2983 * runaway file reclaim problem, but rather just
2984 * extreme pressure. Reclaim as per usual then.
2986 anon
= node_page_state(pgdat
, NR_INACTIVE_ANON
);
2989 file
+ free
<= total_high_wmark
&&
2990 !(sc
->may_deactivate
& DEACTIVATE_ANON
) &&
2991 anon
>> sc
->priority
;
2994 shrink_node_memcgs(pgdat
, sc
);
2996 if (reclaim_state
) {
2997 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2998 reclaim_state
->reclaimed_slab
= 0;
3001 /* Record the subtree's reclaim efficiency */
3002 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
, true,
3003 sc
->nr_scanned
- nr_scanned
,
3004 sc
->nr_reclaimed
- nr_reclaimed
);
3006 if (sc
->nr_reclaimed
- nr_reclaimed
)
3009 if (current_is_kswapd()) {
3011 * If reclaim is isolating dirty pages under writeback,
3012 * it implies that the long-lived page allocation rate
3013 * is exceeding the page laundering rate. Either the
3014 * global limits are not being effective at throttling
3015 * processes due to the page distribution throughout
3016 * zones or there is heavy usage of a slow backing
3017 * device. The only option is to throttle from reclaim
3018 * context which is not ideal as there is no guarantee
3019 * the dirtying process is throttled in the same way
3020 * balance_dirty_pages() manages.
3022 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
3023 * count the number of pages under pages flagged for
3024 * immediate reclaim and stall if any are encountered
3025 * in the nr_immediate check below.
3027 if (sc
->nr
.writeback
&& sc
->nr
.writeback
== sc
->nr
.taken
)
3028 set_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
3030 /* Allow kswapd to start writing pages during reclaim.*/
3031 if (sc
->nr
.unqueued_dirty
== sc
->nr
.file_taken
)
3032 set_bit(PGDAT_DIRTY
, &pgdat
->flags
);
3035 * If kswapd scans pages marked for immediate
3036 * reclaim and under writeback (nr_immediate), it
3037 * implies that pages are cycling through the LRU
3038 * faster than they are written so also forcibly stall.
3040 if (sc
->nr
.immediate
)
3041 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
3045 * Tag a node/memcg as congested if all the dirty pages
3046 * scanned were backed by a congested BDI and
3047 * wait_iff_congested will stall.
3049 * Legacy memcg will stall in page writeback so avoid forcibly
3050 * stalling in wait_iff_congested().
3052 if ((current_is_kswapd() ||
3053 (cgroup_reclaim(sc
) && writeback_throttling_sane(sc
))) &&
3054 sc
->nr
.dirty
&& sc
->nr
.dirty
== sc
->nr
.congested
)
3055 set_bit(LRUVEC_CONGESTED
, &target_lruvec
->flags
);
3058 * Stall direct reclaim for IO completions if underlying BDIs
3059 * and node is congested. Allow kswapd to continue until it
3060 * starts encountering unqueued dirty pages or cycling through
3061 * the LRU too quickly.
3063 if (!current_is_kswapd() && current_may_throttle() &&
3064 !sc
->hibernation_mode
&&
3065 test_bit(LRUVEC_CONGESTED
, &target_lruvec
->flags
))
3066 wait_iff_congested(BLK_RW_ASYNC
, HZ
/10);
3068 if (should_continue_reclaim(pgdat
, sc
->nr_reclaimed
- nr_reclaimed
,
3073 * Kswapd gives up on balancing particular nodes after too
3074 * many failures to reclaim anything from them and goes to
3075 * sleep. On reclaim progress, reset the failure counter. A
3076 * successful direct reclaim run will revive a dormant kswapd.
3079 pgdat
->kswapd_failures
= 0;
3083 * Returns true if compaction should go ahead for a costly-order request, or
3084 * the allocation would already succeed without compaction. Return false if we
3085 * should reclaim first.
3087 static inline bool compaction_ready(struct zone
*zone
, struct scan_control
*sc
)
3089 unsigned long watermark
;
3090 enum compact_result suitable
;
3092 suitable
= compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
);
3093 if (suitable
== COMPACT_SUCCESS
)
3094 /* Allocation should succeed already. Don't reclaim. */
3096 if (suitable
== COMPACT_SKIPPED
)
3097 /* Compaction cannot yet proceed. Do reclaim. */
3101 * Compaction is already possible, but it takes time to run and there
3102 * are potentially other callers using the pages just freed. So proceed
3103 * with reclaim to make a buffer of free pages available to give
3104 * compaction a reasonable chance of completing and allocating the page.
3105 * Note that we won't actually reclaim the whole buffer in one attempt
3106 * as the target watermark in should_continue_reclaim() is lower. But if
3107 * we are already above the high+gap watermark, don't reclaim at all.
3109 watermark
= high_wmark_pages(zone
) + compact_gap(sc
->order
);
3111 return zone_watermark_ok_safe(zone
, 0, watermark
, sc
->reclaim_idx
);
3115 * This is the direct reclaim path, for page-allocating processes. We only
3116 * try to reclaim pages from zones which will satisfy the caller's allocation
3119 * If a zone is deemed to be full of pinned pages then just give it a light
3120 * scan then give up on it.
3122 static void shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
3126 unsigned long nr_soft_reclaimed
;
3127 unsigned long nr_soft_scanned
;
3129 pg_data_t
*last_pgdat
= NULL
;
3132 * If the number of buffer_heads in the machine exceeds the maximum
3133 * allowed level, force direct reclaim to scan the highmem zone as
3134 * highmem pages could be pinning lowmem pages storing buffer_heads
3136 orig_mask
= sc
->gfp_mask
;
3137 if (buffer_heads_over_limit
) {
3138 sc
->gfp_mask
|= __GFP_HIGHMEM
;
3139 sc
->reclaim_idx
= gfp_zone(sc
->gfp_mask
);
3142 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
3143 sc
->reclaim_idx
, sc
->nodemask
) {
3145 * Take care memory controller reclaiming has small influence
3148 if (!cgroup_reclaim(sc
)) {
3149 if (!cpuset_zone_allowed(zone
,
3150 GFP_KERNEL
| __GFP_HARDWALL
))
3154 * If we already have plenty of memory free for
3155 * compaction in this zone, don't free any more.
3156 * Even though compaction is invoked for any
3157 * non-zero order, only frequent costly order
3158 * reclamation is disruptive enough to become a
3159 * noticeable problem, like transparent huge
3162 if (IS_ENABLED(CONFIG_COMPACTION
) &&
3163 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
3164 compaction_ready(zone
, sc
)) {
3165 sc
->compaction_ready
= true;
3170 * Shrink each node in the zonelist once. If the
3171 * zonelist is ordered by zone (not the default) then a
3172 * node may be shrunk multiple times but in that case
3173 * the user prefers lower zones being preserved.
3175 if (zone
->zone_pgdat
== last_pgdat
)
3179 * This steals pages from memory cgroups over softlimit
3180 * and returns the number of reclaimed pages and
3181 * scanned pages. This works for global memory pressure
3182 * and balancing, not for a memcg's limit.
3184 nr_soft_scanned
= 0;
3185 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
->zone_pgdat
,
3186 sc
->order
, sc
->gfp_mask
,
3188 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
3189 sc
->nr_scanned
+= nr_soft_scanned
;
3190 /* need some check for avoid more shrink_zone() */
3193 /* See comment about same check for global reclaim above */
3194 if (zone
->zone_pgdat
== last_pgdat
)
3196 last_pgdat
= zone
->zone_pgdat
;
3197 shrink_node(zone
->zone_pgdat
, sc
);
3201 * Restore to original mask to avoid the impact on the caller if we
3202 * promoted it to __GFP_HIGHMEM.
3204 sc
->gfp_mask
= orig_mask
;
3207 static void snapshot_refaults(struct mem_cgroup
*target_memcg
, pg_data_t
*pgdat
)
3209 struct lruvec
*target_lruvec
;
3210 unsigned long refaults
;
3212 target_lruvec
= mem_cgroup_lruvec(target_memcg
, pgdat
);
3213 refaults
= lruvec_page_state(target_lruvec
, WORKINGSET_ACTIVATE_ANON
);
3214 target_lruvec
->refaults
[0] = refaults
;
3215 refaults
= lruvec_page_state(target_lruvec
, WORKINGSET_ACTIVATE_FILE
);
3216 target_lruvec
->refaults
[1] = refaults
;
3220 * This is the main entry point to direct page reclaim.
3222 * If a full scan of the inactive list fails to free enough memory then we
3223 * are "out of memory" and something needs to be killed.
3225 * If the caller is !__GFP_FS then the probability of a failure is reasonably
3226 * high - the zone may be full of dirty or under-writeback pages, which this
3227 * caller can't do much about. We kick the writeback threads and take explicit
3228 * naps in the hope that some of these pages can be written. But if the
3229 * allocating task holds filesystem locks which prevent writeout this might not
3230 * work, and the allocation attempt will fail.
3232 * returns: 0, if no pages reclaimed
3233 * else, the number of pages reclaimed
3235 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
3236 struct scan_control
*sc
)
3238 int initial_priority
= sc
->priority
;
3239 pg_data_t
*last_pgdat
;
3243 delayacct_freepages_start();
3245 if (!cgroup_reclaim(sc
))
3246 __count_zid_vm_events(ALLOCSTALL
, sc
->reclaim_idx
, 1);
3249 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
3252 shrink_zones(zonelist
, sc
);
3254 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
3257 if (sc
->compaction_ready
)
3261 * If we're getting trouble reclaiming, start doing
3262 * writepage even in laptop mode.
3264 if (sc
->priority
< DEF_PRIORITY
- 2)
3265 sc
->may_writepage
= 1;
3266 } while (--sc
->priority
>= 0);
3269 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
, sc
->reclaim_idx
,
3271 if (zone
->zone_pgdat
== last_pgdat
)
3273 last_pgdat
= zone
->zone_pgdat
;
3275 snapshot_refaults(sc
->target_mem_cgroup
, zone
->zone_pgdat
);
3277 if (cgroup_reclaim(sc
)) {
3278 struct lruvec
*lruvec
;
3280 lruvec
= mem_cgroup_lruvec(sc
->target_mem_cgroup
,
3282 clear_bit(LRUVEC_CONGESTED
, &lruvec
->flags
);
3286 delayacct_freepages_end();
3288 if (sc
->nr_reclaimed
)
3289 return sc
->nr_reclaimed
;
3291 /* Aborted reclaim to try compaction? don't OOM, then */
3292 if (sc
->compaction_ready
)
3296 * We make inactive:active ratio decisions based on the node's
3297 * composition of memory, but a restrictive reclaim_idx or a
3298 * memory.low cgroup setting can exempt large amounts of
3299 * memory from reclaim. Neither of which are very common, so
3300 * instead of doing costly eligibility calculations of the
3301 * entire cgroup subtree up front, we assume the estimates are
3302 * good, and retry with forcible deactivation if that fails.
3304 if (sc
->skipped_deactivate
) {
3305 sc
->priority
= initial_priority
;
3306 sc
->force_deactivate
= 1;
3307 sc
->skipped_deactivate
= 0;
3311 /* Untapped cgroup reserves? Don't OOM, retry. */
3312 if (sc
->memcg_low_skipped
) {
3313 sc
->priority
= initial_priority
;
3314 sc
->force_deactivate
= 0;
3315 sc
->memcg_low_reclaim
= 1;
3316 sc
->memcg_low_skipped
= 0;
3323 static bool allow_direct_reclaim(pg_data_t
*pgdat
)
3326 unsigned long pfmemalloc_reserve
= 0;
3327 unsigned long free_pages
= 0;
3331 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3334 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
3335 zone
= &pgdat
->node_zones
[i
];
3336 if (!managed_zone(zone
))
3339 if (!zone_reclaimable_pages(zone
))
3342 pfmemalloc_reserve
+= min_wmark_pages(zone
);
3343 free_pages
+= zone_page_state(zone
, NR_FREE_PAGES
);
3346 /* If there are no reserves (unexpected config) then do not throttle */
3347 if (!pfmemalloc_reserve
)
3350 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
3352 /* kswapd must be awake if processes are being throttled */
3353 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
3354 if (READ_ONCE(pgdat
->kswapd_highest_zoneidx
) > ZONE_NORMAL
)
3355 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, ZONE_NORMAL
);
3357 wake_up_interruptible(&pgdat
->kswapd_wait
);
3364 * Throttle direct reclaimers if backing storage is backed by the network
3365 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
3366 * depleted. kswapd will continue to make progress and wake the processes
3367 * when the low watermark is reached.
3369 * Returns true if a fatal signal was delivered during throttling. If this
3370 * happens, the page allocator should not consider triggering the OOM killer.
3372 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
3373 nodemask_t
*nodemask
)
3377 pg_data_t
*pgdat
= NULL
;
3380 * Kernel threads should not be throttled as they may be indirectly
3381 * responsible for cleaning pages necessary for reclaim to make forward
3382 * progress. kjournald for example may enter direct reclaim while
3383 * committing a transaction where throttling it could forcing other
3384 * processes to block on log_wait_commit().
3386 if (current
->flags
& PF_KTHREAD
)
3390 * If a fatal signal is pending, this process should not throttle.
3391 * It should return quickly so it can exit and free its memory
3393 if (fatal_signal_pending(current
))
3397 * Check if the pfmemalloc reserves are ok by finding the first node
3398 * with a usable ZONE_NORMAL or lower zone. The expectation is that
3399 * GFP_KERNEL will be required for allocating network buffers when
3400 * swapping over the network so ZONE_HIGHMEM is unusable.
3402 * Throttling is based on the first usable node and throttled processes
3403 * wait on a queue until kswapd makes progress and wakes them. There
3404 * is an affinity then between processes waking up and where reclaim
3405 * progress has been made assuming the process wakes on the same node.
3406 * More importantly, processes running on remote nodes will not compete
3407 * for remote pfmemalloc reserves and processes on different nodes
3408 * should make reasonable progress.
3410 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
3411 gfp_zone(gfp_mask
), nodemask
) {
3412 if (zone_idx(zone
) > ZONE_NORMAL
)
3415 /* Throttle based on the first usable node */
3416 pgdat
= zone
->zone_pgdat
;
3417 if (allow_direct_reclaim(pgdat
))
3422 /* If no zone was usable by the allocation flags then do not throttle */
3426 /* Account for the throttling */
3427 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
3430 * If the caller cannot enter the filesystem, it's possible that it
3431 * is due to the caller holding an FS lock or performing a journal
3432 * transaction in the case of a filesystem like ext[3|4]. In this case,
3433 * it is not safe to block on pfmemalloc_wait as kswapd could be
3434 * blocked waiting on the same lock. Instead, throttle for up to a
3435 * second before continuing.
3437 if (!(gfp_mask
& __GFP_FS
)) {
3438 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
3439 allow_direct_reclaim(pgdat
), HZ
);
3444 /* Throttle until kswapd wakes the process */
3445 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
3446 allow_direct_reclaim(pgdat
));
3449 if (fatal_signal_pending(current
))
3456 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
3457 gfp_t gfp_mask
, nodemask_t
*nodemask
)
3459 unsigned long nr_reclaimed
;
3460 struct scan_control sc
= {
3461 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
3462 .gfp_mask
= current_gfp_context(gfp_mask
),
3463 .reclaim_idx
= gfp_zone(gfp_mask
),
3465 .nodemask
= nodemask
,
3466 .priority
= DEF_PRIORITY
,
3467 .may_writepage
= !laptop_mode
,
3473 * scan_control uses s8 fields for order, priority, and reclaim_idx.
3474 * Confirm they are large enough for max values.
3476 BUILD_BUG_ON(MAX_ORDER
> S8_MAX
);
3477 BUILD_BUG_ON(DEF_PRIORITY
> S8_MAX
);
3478 BUILD_BUG_ON(MAX_NR_ZONES
> S8_MAX
);
3481 * Do not enter reclaim if fatal signal was delivered while throttled.
3482 * 1 is returned so that the page allocator does not OOM kill at this
3485 if (throttle_direct_reclaim(sc
.gfp_mask
, zonelist
, nodemask
))
3488 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3489 trace_mm_vmscan_direct_reclaim_begin(order
, sc
.gfp_mask
);
3491 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3493 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
3494 set_task_reclaim_state(current
, NULL
);
3496 return nr_reclaimed
;
3501 /* Only used by soft limit reclaim. Do not reuse for anything else. */
3502 unsigned long mem_cgroup_shrink_node(struct mem_cgroup
*memcg
,
3503 gfp_t gfp_mask
, bool noswap
,
3505 unsigned long *nr_scanned
)
3507 struct lruvec
*lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
3508 struct scan_control sc
= {
3509 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
3510 .target_mem_cgroup
= memcg
,
3511 .may_writepage
= !laptop_mode
,
3513 .reclaim_idx
= MAX_NR_ZONES
- 1,
3514 .may_swap
= !noswap
,
3517 WARN_ON_ONCE(!current
->reclaim_state
);
3519 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
3520 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
3522 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
3526 * NOTE: Although we can get the priority field, using it
3527 * here is not a good idea, since it limits the pages we can scan.
3528 * if we don't reclaim here, the shrink_node from balance_pgdat
3529 * will pick up pages from other mem cgroup's as well. We hack
3530 * the priority and make it zero.
3532 shrink_lruvec(lruvec
, &sc
);
3534 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
3536 *nr_scanned
= sc
.nr_scanned
;
3538 return sc
.nr_reclaimed
;
3541 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
3542 unsigned long nr_pages
,
3546 unsigned long nr_reclaimed
;
3547 unsigned int noreclaim_flag
;
3548 struct scan_control sc
= {
3549 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
3550 .gfp_mask
= (current_gfp_context(gfp_mask
) & GFP_RECLAIM_MASK
) |
3551 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
3552 .reclaim_idx
= MAX_NR_ZONES
- 1,
3553 .target_mem_cgroup
= memcg
,
3554 .priority
= DEF_PRIORITY
,
3555 .may_writepage
= !laptop_mode
,
3557 .may_swap
= may_swap
,
3560 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
3561 * equal pressure on all the nodes. This is based on the assumption that
3562 * the reclaim does not bail out early.
3564 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3566 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3567 trace_mm_vmscan_memcg_reclaim_begin(0, sc
.gfp_mask
);
3568 noreclaim_flag
= memalloc_noreclaim_save();
3570 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3572 memalloc_noreclaim_restore(noreclaim_flag
);
3573 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
3574 set_task_reclaim_state(current
, NULL
);
3576 return nr_reclaimed
;
3580 static void age_active_anon(struct pglist_data
*pgdat
,
3581 struct scan_control
*sc
)
3583 struct mem_cgroup
*memcg
;
3584 struct lruvec
*lruvec
;
3586 if (!total_swap_pages
)
3589 lruvec
= mem_cgroup_lruvec(NULL
, pgdat
);
3590 if (!inactive_is_low(lruvec
, LRU_INACTIVE_ANON
))
3593 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
3595 lruvec
= mem_cgroup_lruvec(memcg
, pgdat
);
3596 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
3597 sc
, LRU_ACTIVE_ANON
);
3598 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
3602 static bool pgdat_watermark_boosted(pg_data_t
*pgdat
, int highest_zoneidx
)
3608 * Check for watermark boosts top-down as the higher zones
3609 * are more likely to be boosted. Both watermarks and boosts
3610 * should not be checked at the same time as reclaim would
3611 * start prematurely when there is no boosting and a lower
3614 for (i
= highest_zoneidx
; i
>= 0; i
--) {
3615 zone
= pgdat
->node_zones
+ i
;
3616 if (!managed_zone(zone
))
3619 if (zone
->watermark_boost
)
3627 * Returns true if there is an eligible zone balanced for the request order
3628 * and highest_zoneidx
3630 static bool pgdat_balanced(pg_data_t
*pgdat
, int order
, int highest_zoneidx
)
3633 unsigned long mark
= -1;
3637 * Check watermarks bottom-up as lower zones are more likely to
3640 for (i
= 0; i
<= highest_zoneidx
; i
++) {
3641 zone
= pgdat
->node_zones
+ i
;
3643 if (!managed_zone(zone
))
3646 mark
= high_wmark_pages(zone
);
3647 if (zone_watermark_ok_safe(zone
, order
, mark
, highest_zoneidx
))
3652 * If a node has no populated zone within highest_zoneidx, it does not
3653 * need balancing by definition. This can happen if a zone-restricted
3654 * allocation tries to wake a remote kswapd.
3662 /* Clear pgdat state for congested, dirty or under writeback. */
3663 static void clear_pgdat_congested(pg_data_t
*pgdat
)
3665 struct lruvec
*lruvec
= mem_cgroup_lruvec(NULL
, pgdat
);
3667 clear_bit(LRUVEC_CONGESTED
, &lruvec
->flags
);
3668 clear_bit(PGDAT_DIRTY
, &pgdat
->flags
);
3669 clear_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
3673 * Prepare kswapd for sleeping. This verifies that there are no processes
3674 * waiting in throttle_direct_reclaim() and that watermarks have been met.
3676 * Returns true if kswapd is ready to sleep
3678 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
,
3679 int highest_zoneidx
)
3682 * The throttled processes are normally woken up in balance_pgdat() as
3683 * soon as allow_direct_reclaim() is true. But there is a potential
3684 * race between when kswapd checks the watermarks and a process gets
3685 * throttled. There is also a potential race if processes get
3686 * throttled, kswapd wakes, a large process exits thereby balancing the
3687 * zones, which causes kswapd to exit balance_pgdat() before reaching
3688 * the wake up checks. If kswapd is going to sleep, no process should
3689 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
3690 * the wake up is premature, processes will wake kswapd and get
3691 * throttled again. The difference from wake ups in balance_pgdat() is
3692 * that here we are under prepare_to_wait().
3694 if (waitqueue_active(&pgdat
->pfmemalloc_wait
))
3695 wake_up_all(&pgdat
->pfmemalloc_wait
);
3697 /* Hopeless node, leave it to direct reclaim */
3698 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3701 if (pgdat_balanced(pgdat
, order
, highest_zoneidx
)) {
3702 clear_pgdat_congested(pgdat
);
3710 * kswapd shrinks a node of pages that are at or below the highest usable
3711 * zone that is currently unbalanced.
3713 * Returns true if kswapd scanned at least the requested number of pages to
3714 * reclaim or if the lack of progress was due to pages under writeback.
3715 * This is used to determine if the scanning priority needs to be raised.
3717 static bool kswapd_shrink_node(pg_data_t
*pgdat
,
3718 struct scan_control
*sc
)
3723 /* Reclaim a number of pages proportional to the number of zones */
3724 sc
->nr_to_reclaim
= 0;
3725 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
3726 zone
= pgdat
->node_zones
+ z
;
3727 if (!managed_zone(zone
))
3730 sc
->nr_to_reclaim
+= max(high_wmark_pages(zone
), SWAP_CLUSTER_MAX
);
3734 * Historically care was taken to put equal pressure on all zones but
3735 * now pressure is applied based on node LRU order.
3737 shrink_node(pgdat
, sc
);
3740 * Fragmentation may mean that the system cannot be rebalanced for
3741 * high-order allocations. If twice the allocation size has been
3742 * reclaimed then recheck watermarks only at order-0 to prevent
3743 * excessive reclaim. Assume that a process requested a high-order
3744 * can direct reclaim/compact.
3746 if (sc
->order
&& sc
->nr_reclaimed
>= compact_gap(sc
->order
))
3749 return sc
->nr_scanned
>= sc
->nr_to_reclaim
;
3752 /* Page allocator PCP high watermark is lowered if reclaim is active. */
3754 update_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
, bool active
)
3759 for (i
= 0; i
<= highest_zoneidx
; i
++) {
3760 zone
= pgdat
->node_zones
+ i
;
3762 if (!managed_zone(zone
))
3766 set_bit(ZONE_RECLAIM_ACTIVE
, &zone
->flags
);
3768 clear_bit(ZONE_RECLAIM_ACTIVE
, &zone
->flags
);
3773 set_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
)
3775 update_reclaim_active(pgdat
, highest_zoneidx
, true);
3779 clear_reclaim_active(pg_data_t
*pgdat
, int highest_zoneidx
)
3781 update_reclaim_active(pgdat
, highest_zoneidx
, false);
3785 * For kswapd, balance_pgdat() will reclaim pages across a node from zones
3786 * that are eligible for use by the caller until at least one zone is
3789 * Returns the order kswapd finished reclaiming at.
3791 * kswapd scans the zones in the highmem->normal->dma direction. It skips
3792 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
3793 * found to have free_pages <= high_wmark_pages(zone), any page in that zone
3794 * or lower is eligible for reclaim until at least one usable zone is
3797 static int balance_pgdat(pg_data_t
*pgdat
, int order
, int highest_zoneidx
)
3800 unsigned long nr_soft_reclaimed
;
3801 unsigned long nr_soft_scanned
;
3802 unsigned long pflags
;
3803 unsigned long nr_boost_reclaim
;
3804 unsigned long zone_boosts
[MAX_NR_ZONES
] = { 0, };
3807 struct scan_control sc
= {
3808 .gfp_mask
= GFP_KERNEL
,
3813 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3814 psi_memstall_enter(&pflags
);
3815 __fs_reclaim_acquire();
3817 count_vm_event(PAGEOUTRUN
);
3820 * Account for the reclaim boost. Note that the zone boost is left in
3821 * place so that parallel allocations that are near the watermark will
3822 * stall or direct reclaim until kswapd is finished.
3824 nr_boost_reclaim
= 0;
3825 for (i
= 0; i
<= highest_zoneidx
; i
++) {
3826 zone
= pgdat
->node_zones
+ i
;
3827 if (!managed_zone(zone
))
3830 nr_boost_reclaim
+= zone
->watermark_boost
;
3831 zone_boosts
[i
] = zone
->watermark_boost
;
3833 boosted
= nr_boost_reclaim
;
3836 set_reclaim_active(pgdat
, highest_zoneidx
);
3837 sc
.priority
= DEF_PRIORITY
;
3839 unsigned long nr_reclaimed
= sc
.nr_reclaimed
;
3840 bool raise_priority
= true;
3844 sc
.reclaim_idx
= highest_zoneidx
;
3847 * If the number of buffer_heads exceeds the maximum allowed
3848 * then consider reclaiming from all zones. This has a dual
3849 * purpose -- on 64-bit systems it is expected that
3850 * buffer_heads are stripped during active rotation. On 32-bit
3851 * systems, highmem pages can pin lowmem memory and shrinking
3852 * buffers can relieve lowmem pressure. Reclaim may still not
3853 * go ahead if all eligible zones for the original allocation
3854 * request are balanced to avoid excessive reclaim from kswapd.
3856 if (buffer_heads_over_limit
) {
3857 for (i
= MAX_NR_ZONES
- 1; i
>= 0; i
--) {
3858 zone
= pgdat
->node_zones
+ i
;
3859 if (!managed_zone(zone
))
3868 * If the pgdat is imbalanced then ignore boosting and preserve
3869 * the watermarks for a later time and restart. Note that the
3870 * zone watermarks will be still reset at the end of balancing
3871 * on the grounds that the normal reclaim should be enough to
3872 * re-evaluate if boosting is required when kswapd next wakes.
3874 balanced
= pgdat_balanced(pgdat
, sc
.order
, highest_zoneidx
);
3875 if (!balanced
&& nr_boost_reclaim
) {
3876 nr_boost_reclaim
= 0;
3881 * If boosting is not active then only reclaim if there are no
3882 * eligible zones. Note that sc.reclaim_idx is not used as
3883 * buffer_heads_over_limit may have adjusted it.
3885 if (!nr_boost_reclaim
&& balanced
)
3888 /* Limit the priority of boosting to avoid reclaim writeback */
3889 if (nr_boost_reclaim
&& sc
.priority
== DEF_PRIORITY
- 2)
3890 raise_priority
= false;
3893 * Do not writeback or swap pages for boosted reclaim. The
3894 * intent is to relieve pressure not issue sub-optimal IO
3895 * from reclaim context. If no pages are reclaimed, the
3896 * reclaim will be aborted.
3898 sc
.may_writepage
= !laptop_mode
&& !nr_boost_reclaim
;
3899 sc
.may_swap
= !nr_boost_reclaim
;
3902 * Do some background aging of the anon list, to give
3903 * pages a chance to be referenced before reclaiming. All
3904 * pages are rotated regardless of classzone as this is
3905 * about consistent aging.
3907 age_active_anon(pgdat
, &sc
);
3910 * If we're getting trouble reclaiming, start doing writepage
3911 * even in laptop mode.
3913 if (sc
.priority
< DEF_PRIORITY
- 2)
3914 sc
.may_writepage
= 1;
3916 /* Call soft limit reclaim before calling shrink_node. */
3918 nr_soft_scanned
= 0;
3919 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(pgdat
, sc
.order
,
3920 sc
.gfp_mask
, &nr_soft_scanned
);
3921 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
3924 * There should be no need to raise the scanning priority if
3925 * enough pages are already being scanned that that high
3926 * watermark would be met at 100% efficiency.
3928 if (kswapd_shrink_node(pgdat
, &sc
))
3929 raise_priority
= false;
3932 * If the low watermark is met there is no need for processes
3933 * to be throttled on pfmemalloc_wait as they should not be
3934 * able to safely make forward progress. Wake them
3936 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
3937 allow_direct_reclaim(pgdat
))
3938 wake_up_all(&pgdat
->pfmemalloc_wait
);
3940 /* Check if kswapd should be suspending */
3941 __fs_reclaim_release();
3942 ret
= try_to_freeze();
3943 __fs_reclaim_acquire();
3944 if (ret
|| kthread_should_stop())
3948 * Raise priority if scanning rate is too low or there was no
3949 * progress in reclaiming pages
3951 nr_reclaimed
= sc
.nr_reclaimed
- nr_reclaimed
;
3952 nr_boost_reclaim
-= min(nr_boost_reclaim
, nr_reclaimed
);
3955 * If reclaim made no progress for a boost, stop reclaim as
3956 * IO cannot be queued and it could be an infinite loop in
3957 * extreme circumstances.
3959 if (nr_boost_reclaim
&& !nr_reclaimed
)
3962 if (raise_priority
|| !nr_reclaimed
)
3964 } while (sc
.priority
>= 1);
3966 if (!sc
.nr_reclaimed
)
3967 pgdat
->kswapd_failures
++;
3970 clear_reclaim_active(pgdat
, highest_zoneidx
);
3972 /* If reclaim was boosted, account for the reclaim done in this pass */
3974 unsigned long flags
;
3976 for (i
= 0; i
<= highest_zoneidx
; i
++) {
3977 if (!zone_boosts
[i
])
3980 /* Increments are under the zone lock */
3981 zone
= pgdat
->node_zones
+ i
;
3982 spin_lock_irqsave(&zone
->lock
, flags
);
3983 zone
->watermark_boost
-= min(zone
->watermark_boost
, zone_boosts
[i
]);
3984 spin_unlock_irqrestore(&zone
->lock
, flags
);
3988 * As there is now likely space, wakeup kcompact to defragment
3991 wakeup_kcompactd(pgdat
, pageblock_order
, highest_zoneidx
);
3994 snapshot_refaults(NULL
, pgdat
);
3995 __fs_reclaim_release();
3996 psi_memstall_leave(&pflags
);
3997 set_task_reclaim_state(current
, NULL
);
4000 * Return the order kswapd stopped reclaiming at as
4001 * prepare_kswapd_sleep() takes it into account. If another caller
4002 * entered the allocator slow path while kswapd was awake, order will
4003 * remain at the higher level.
4009 * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
4010 * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
4011 * not a valid index then either kswapd runs for first time or kswapd couldn't
4012 * sleep after previous reclaim attempt (node is still unbalanced). In that
4013 * case return the zone index of the previous kswapd reclaim cycle.
4015 static enum zone_type
kswapd_highest_zoneidx(pg_data_t
*pgdat
,
4016 enum zone_type prev_highest_zoneidx
)
4018 enum zone_type curr_idx
= READ_ONCE(pgdat
->kswapd_highest_zoneidx
);
4020 return curr_idx
== MAX_NR_ZONES
? prev_highest_zoneidx
: curr_idx
;
4023 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int alloc_order
, int reclaim_order
,
4024 unsigned int highest_zoneidx
)
4029 if (freezing(current
) || kthread_should_stop())
4032 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
4035 * Try to sleep for a short interval. Note that kcompactd will only be
4036 * woken if it is possible to sleep for a short interval. This is
4037 * deliberate on the assumption that if reclaim cannot keep an
4038 * eligible zone balanced that it's also unlikely that compaction will
4041 if (prepare_kswapd_sleep(pgdat
, reclaim_order
, highest_zoneidx
)) {
4043 * Compaction records what page blocks it recently failed to
4044 * isolate pages from and skips them in the future scanning.
4045 * When kswapd is going to sleep, it is reasonable to assume
4046 * that pages and compaction may succeed so reset the cache.
4048 reset_isolation_suitable(pgdat
);
4051 * We have freed the memory, now we should compact it to make
4052 * allocation of the requested order possible.
4054 wakeup_kcompactd(pgdat
, alloc_order
, highest_zoneidx
);
4056 remaining
= schedule_timeout(HZ
/10);
4059 * If woken prematurely then reset kswapd_highest_zoneidx and
4060 * order. The values will either be from a wakeup request or
4061 * the previous request that slept prematurely.
4064 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
,
4065 kswapd_highest_zoneidx(pgdat
,
4068 if (READ_ONCE(pgdat
->kswapd_order
) < reclaim_order
)
4069 WRITE_ONCE(pgdat
->kswapd_order
, reclaim_order
);
4072 finish_wait(&pgdat
->kswapd_wait
, &wait
);
4073 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
4077 * After a short sleep, check if it was a premature sleep. If not, then
4078 * go fully to sleep until explicitly woken up.
4081 prepare_kswapd_sleep(pgdat
, reclaim_order
, highest_zoneidx
)) {
4082 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
4085 * vmstat counters are not perfectly accurate and the estimated
4086 * value for counters such as NR_FREE_PAGES can deviate from the
4087 * true value by nr_online_cpus * threshold. To avoid the zone
4088 * watermarks being breached while under pressure, we reduce the
4089 * per-cpu vmstat threshold while kswapd is awake and restore
4090 * them before going back to sleep.
4092 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
4094 if (!kthread_should_stop())
4097 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
4100 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
4102 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
4104 finish_wait(&pgdat
->kswapd_wait
, &wait
);
4108 * The background pageout daemon, started as a kernel thread
4109 * from the init process.
4111 * This basically trickles out pages so that we have _some_
4112 * free memory available even if there is no other activity
4113 * that frees anything up. This is needed for things like routing
4114 * etc, where we otherwise might have all activity going on in
4115 * asynchronous contexts that cannot page things out.
4117 * If there are applications that are active memory-allocators
4118 * (most normal use), this basically shouldn't matter.
4120 static int kswapd(void *p
)
4122 unsigned int alloc_order
, reclaim_order
;
4123 unsigned int highest_zoneidx
= MAX_NR_ZONES
- 1;
4124 pg_data_t
*pgdat
= (pg_data_t
*)p
;
4125 struct task_struct
*tsk
= current
;
4126 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
4128 if (!cpumask_empty(cpumask
))
4129 set_cpus_allowed_ptr(tsk
, cpumask
);
4132 * Tell the memory management that we're a "memory allocator",
4133 * and that if we need more memory we should get access to it
4134 * regardless (see "__alloc_pages()"). "kswapd" should
4135 * never get caught in the normal page freeing logic.
4137 * (Kswapd normally doesn't need memory anyway, but sometimes
4138 * you need a small amount of memory in order to be able to
4139 * page out something else, and this flag essentially protects
4140 * us from recursively trying to free more memory as we're
4141 * trying to free the first piece of memory in the first place).
4143 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
4146 WRITE_ONCE(pgdat
->kswapd_order
, 0);
4147 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, MAX_NR_ZONES
);
4151 alloc_order
= reclaim_order
= READ_ONCE(pgdat
->kswapd_order
);
4152 highest_zoneidx
= kswapd_highest_zoneidx(pgdat
,
4156 kswapd_try_to_sleep(pgdat
, alloc_order
, reclaim_order
,
4159 /* Read the new order and highest_zoneidx */
4160 alloc_order
= READ_ONCE(pgdat
->kswapd_order
);
4161 highest_zoneidx
= kswapd_highest_zoneidx(pgdat
,
4163 WRITE_ONCE(pgdat
->kswapd_order
, 0);
4164 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, MAX_NR_ZONES
);
4166 ret
= try_to_freeze();
4167 if (kthread_should_stop())
4171 * We can speed up thawing tasks if we don't call balance_pgdat
4172 * after returning from the refrigerator
4178 * Reclaim begins at the requested order but if a high-order
4179 * reclaim fails then kswapd falls back to reclaiming for
4180 * order-0. If that happens, kswapd will consider sleeping
4181 * for the order it finished reclaiming at (reclaim_order)
4182 * but kcompactd is woken to compact for the original
4183 * request (alloc_order).
4185 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, highest_zoneidx
,
4187 reclaim_order
= balance_pgdat(pgdat
, alloc_order
,
4189 if (reclaim_order
< alloc_order
)
4190 goto kswapd_try_sleep
;
4193 tsk
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
);
4199 * A zone is low on free memory or too fragmented for high-order memory. If
4200 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
4201 * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim
4202 * has failed or is not needed, still wake up kcompactd if only compaction is
4205 void wakeup_kswapd(struct zone
*zone
, gfp_t gfp_flags
, int order
,
4206 enum zone_type highest_zoneidx
)
4209 enum zone_type curr_idx
;
4211 if (!managed_zone(zone
))
4214 if (!cpuset_zone_allowed(zone
, gfp_flags
))
4217 pgdat
= zone
->zone_pgdat
;
4218 curr_idx
= READ_ONCE(pgdat
->kswapd_highest_zoneidx
);
4220 if (curr_idx
== MAX_NR_ZONES
|| curr_idx
< highest_zoneidx
)
4221 WRITE_ONCE(pgdat
->kswapd_highest_zoneidx
, highest_zoneidx
);
4223 if (READ_ONCE(pgdat
->kswapd_order
) < order
)
4224 WRITE_ONCE(pgdat
->kswapd_order
, order
);
4226 if (!waitqueue_active(&pgdat
->kswapd_wait
))
4229 /* Hopeless node, leave it to direct reclaim if possible */
4230 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
||
4231 (pgdat_balanced(pgdat
, order
, highest_zoneidx
) &&
4232 !pgdat_watermark_boosted(pgdat
, highest_zoneidx
))) {
4234 * There may be plenty of free memory available, but it's too
4235 * fragmented for high-order allocations. Wake up kcompactd
4236 * and rely on compaction_suitable() to determine if it's
4237 * needed. If it fails, it will defer subsequent attempts to
4238 * ratelimit its work.
4240 if (!(gfp_flags
& __GFP_DIRECT_RECLAIM
))
4241 wakeup_kcompactd(pgdat
, order
, highest_zoneidx
);
4245 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, highest_zoneidx
, order
,
4247 wake_up_interruptible(&pgdat
->kswapd_wait
);
4250 #ifdef CONFIG_HIBERNATION
4252 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
4255 * Rather than trying to age LRUs the aim is to preserve the overall
4256 * LRU order by reclaiming preferentially
4257 * inactive > active > active referenced > active mapped
4259 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
4261 struct scan_control sc
= {
4262 .nr_to_reclaim
= nr_to_reclaim
,
4263 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
4264 .reclaim_idx
= MAX_NR_ZONES
- 1,
4265 .priority
= DEF_PRIORITY
,
4269 .hibernation_mode
= 1,
4271 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
4272 unsigned long nr_reclaimed
;
4273 unsigned int noreclaim_flag
;
4275 fs_reclaim_acquire(sc
.gfp_mask
);
4276 noreclaim_flag
= memalloc_noreclaim_save();
4277 set_task_reclaim_state(current
, &sc
.reclaim_state
);
4279 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
4281 set_task_reclaim_state(current
, NULL
);
4282 memalloc_noreclaim_restore(noreclaim_flag
);
4283 fs_reclaim_release(sc
.gfp_mask
);
4285 return nr_reclaimed
;
4287 #endif /* CONFIG_HIBERNATION */
4290 * This kswapd start function will be called by init and node-hot-add.
4291 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
4293 int kswapd_run(int nid
)
4295 pg_data_t
*pgdat
= NODE_DATA(nid
);
4301 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
4302 if (IS_ERR(pgdat
->kswapd
)) {
4303 /* failure at boot is fatal */
4304 BUG_ON(system_state
< SYSTEM_RUNNING
);
4305 pr_err("Failed to start kswapd on node %d\n", nid
);
4306 ret
= PTR_ERR(pgdat
->kswapd
);
4307 pgdat
->kswapd
= NULL
;
4313 * Called by memory hotplug when all memory in a node is offlined. Caller must
4314 * hold mem_hotplug_begin/end().
4316 void kswapd_stop(int nid
)
4318 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
4321 kthread_stop(kswapd
);
4322 NODE_DATA(nid
)->kswapd
= NULL
;
4326 static int __init
kswapd_init(void)
4331 for_each_node_state(nid
, N_MEMORY
)
4336 module_init(kswapd_init
)
4342 * If non-zero call node_reclaim when the number of free pages falls below
4345 int node_reclaim_mode __read_mostly
;
4348 * Priority for NODE_RECLAIM. This determines the fraction of pages
4349 * of a node considered for each zone_reclaim. 4 scans 1/16th of
4352 #define NODE_RECLAIM_PRIORITY 4
4355 * Percentage of pages in a zone that must be unmapped for node_reclaim to
4358 int sysctl_min_unmapped_ratio
= 1;
4361 * If the number of slab pages in a zone grows beyond this percentage then
4362 * slab reclaim needs to occur.
4364 int sysctl_min_slab_ratio
= 5;
4366 static inline unsigned long node_unmapped_file_pages(struct pglist_data
*pgdat
)
4368 unsigned long file_mapped
= node_page_state(pgdat
, NR_FILE_MAPPED
);
4369 unsigned long file_lru
= node_page_state(pgdat
, NR_INACTIVE_FILE
) +
4370 node_page_state(pgdat
, NR_ACTIVE_FILE
);
4373 * It's possible for there to be more file mapped pages than
4374 * accounted for by the pages on the file LRU lists because
4375 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
4377 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
4380 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
4381 static unsigned long node_pagecache_reclaimable(struct pglist_data
*pgdat
)
4383 unsigned long nr_pagecache_reclaimable
;
4384 unsigned long delta
= 0;
4387 * If RECLAIM_UNMAP is set, then all file pages are considered
4388 * potentially reclaimable. Otherwise, we have to worry about
4389 * pages like swapcache and node_unmapped_file_pages() provides
4392 if (node_reclaim_mode
& RECLAIM_UNMAP
)
4393 nr_pagecache_reclaimable
= node_page_state(pgdat
, NR_FILE_PAGES
);
4395 nr_pagecache_reclaimable
= node_unmapped_file_pages(pgdat
);
4397 /* If we can't clean pages, remove dirty pages from consideration */
4398 if (!(node_reclaim_mode
& RECLAIM_WRITE
))
4399 delta
+= node_page_state(pgdat
, NR_FILE_DIRTY
);
4401 /* Watch for any possible underflows due to delta */
4402 if (unlikely(delta
> nr_pagecache_reclaimable
))
4403 delta
= nr_pagecache_reclaimable
;
4405 return nr_pagecache_reclaimable
- delta
;
4409 * Try to free up some pages from this node through reclaim.
4411 static int __node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
4413 /* Minimum pages needed in order to stay on node */
4414 const unsigned long nr_pages
= 1 << order
;
4415 struct task_struct
*p
= current
;
4416 unsigned int noreclaim_flag
;
4417 struct scan_control sc
= {
4418 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
4419 .gfp_mask
= current_gfp_context(gfp_mask
),
4421 .priority
= NODE_RECLAIM_PRIORITY
,
4422 .may_writepage
= !!(node_reclaim_mode
& RECLAIM_WRITE
),
4423 .may_unmap
= !!(node_reclaim_mode
& RECLAIM_UNMAP
),
4425 .reclaim_idx
= gfp_zone(gfp_mask
),
4427 unsigned long pflags
;
4429 trace_mm_vmscan_node_reclaim_begin(pgdat
->node_id
, order
,
4433 psi_memstall_enter(&pflags
);
4434 fs_reclaim_acquire(sc
.gfp_mask
);
4436 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
4437 * and we also need to be able to write out pages for RECLAIM_WRITE
4438 * and RECLAIM_UNMAP.
4440 noreclaim_flag
= memalloc_noreclaim_save();
4441 p
->flags
|= PF_SWAPWRITE
;
4442 set_task_reclaim_state(p
, &sc
.reclaim_state
);
4444 if (node_pagecache_reclaimable(pgdat
) > pgdat
->min_unmapped_pages
) {
4446 * Free memory by calling shrink node with increasing
4447 * priorities until we have enough memory freed.
4450 shrink_node(pgdat
, &sc
);
4451 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
4454 set_task_reclaim_state(p
, NULL
);
4455 current
->flags
&= ~PF_SWAPWRITE
;
4456 memalloc_noreclaim_restore(noreclaim_flag
);
4457 fs_reclaim_release(sc
.gfp_mask
);
4458 psi_memstall_leave(&pflags
);
4460 trace_mm_vmscan_node_reclaim_end(sc
.nr_reclaimed
);
4462 return sc
.nr_reclaimed
>= nr_pages
;
4465 int node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
4470 * Node reclaim reclaims unmapped file backed pages and
4471 * slab pages if we are over the defined limits.
4473 * A small portion of unmapped file backed pages is needed for
4474 * file I/O otherwise pages read by file I/O will be immediately
4475 * thrown out if the node is overallocated. So we do not reclaim
4476 * if less than a specified percentage of the node is used by
4477 * unmapped file backed pages.
4479 if (node_pagecache_reclaimable(pgdat
) <= pgdat
->min_unmapped_pages
&&
4480 node_page_state_pages(pgdat
, NR_SLAB_RECLAIMABLE_B
) <=
4481 pgdat
->min_slab_pages
)
4482 return NODE_RECLAIM_FULL
;
4485 * Do not scan if the allocation should not be delayed.
4487 if (!gfpflags_allow_blocking(gfp_mask
) || (current
->flags
& PF_MEMALLOC
))
4488 return NODE_RECLAIM_NOSCAN
;
4491 * Only run node reclaim on the local node or on nodes that do not
4492 * have associated processors. This will favor the local processor
4493 * over remote processors and spread off node memory allocations
4494 * as wide as possible.
4496 if (node_state(pgdat
->node_id
, N_CPU
) && pgdat
->node_id
!= numa_node_id())
4497 return NODE_RECLAIM_NOSCAN
;
4499 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
))
4500 return NODE_RECLAIM_NOSCAN
;
4502 ret
= __node_reclaim(pgdat
, gfp_mask
, order
);
4503 clear_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
);
4506 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
4513 * check_move_unevictable_pages - check pages for evictability and move to
4514 * appropriate zone lru list
4515 * @pvec: pagevec with lru pages to check
4517 * Checks pages for evictability, if an evictable page is in the unevictable
4518 * lru list, moves it to the appropriate evictable lru list. This function
4519 * should be only used for lru pages.
4521 void check_move_unevictable_pages(struct pagevec
*pvec
)
4523 struct lruvec
*lruvec
= NULL
;
4528 for (i
= 0; i
< pvec
->nr
; i
++) {
4529 struct page
*page
= pvec
->pages
[i
];
4532 if (PageTransTail(page
))
4535 nr_pages
= thp_nr_pages(page
);
4536 pgscanned
+= nr_pages
;
4538 /* block memcg migration during page moving between lru */
4539 if (!TestClearPageLRU(page
))
4542 lruvec
= relock_page_lruvec_irq(page
, lruvec
);
4543 if (page_evictable(page
) && PageUnevictable(page
)) {
4544 del_page_from_lru_list(page
, lruvec
);
4545 ClearPageUnevictable(page
);
4546 add_page_to_lru_list(page
, lruvec
);
4547 pgrescued
+= nr_pages
;
4553 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
4554 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
4555 unlock_page_lruvec_irq(lruvec
);
4556 } else if (pgscanned
) {
4557 count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
4560 EXPORT_SYMBOL_GPL(check_move_unevictable_pages
);